Overnight Sourdough Chocolate Cake with Rich Frosting Recipe

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This Overnight Sourdough Chocolate Cake isn’t just another dessert—it’s a showstopper! The sourdough discard adds a subtle tang and moist texture, while the rich chocolate flavor, enhanced by cocoa powder and optional coffee, creates a depth of flavor that’s irresistible. The overnight fermentation not only develops the flavor but also makes the cake easier to digest. Topped with a silky chocolate frosting, this cake is perfect for birthdays, holidays, or any time you crave something indulgent. Plus, it’s surprisingly simple to make, with ingredients you likely already have on hand!

Equipment

Before you start, gather these essential tools to ensure a smooth baking process:

Large mixing bowls (for batter and fermentation)
Whisk or electric mixer (for beating eggs and mixing batter)
Measuring cups and spoons (for precise ingredient measurements)
Bundt pan (for a beautiful cake shape)
Saucepan (for making the frosting)
Spatula (for folding and spreading frosting)
Toothpick (to test doneness)
Oven mitts (for safe handling)
Cooling rack (for cooling the cake)

What you will need?

Here’s everything you’ll need to create this delicious cake, along with substitutions and uses for each ingredient.

Cake Ingredients:

2 1/4 cups (280g) all-purpose flour 🍞
Use: Forms the structure of the cake.
Substitutions: Substitute with gluten-free flour blend (1:1 ratio) for a gluten-free option, or cake flour for a lighter texture.
1 cup (250g) cold milk 🥛
Use: Adds moisture and helps activate the sourdough.
Substitutions: Use almond milk, oat milk, or any plant-based milk for a dairy-free version.
1/4 cup (20g) cocoa powder 🍫
Use: Provides deep chocolate flavor and color.
Substitutions: Dutch-processed cocoa for a richer taste, or carob powder for a caffeine-free alternative.
1/4 cup (50g) sourdough discard or active starter 🍞
Use: Adds a tangy flavor and improves texture through fermentation.
Substitutions: If you don’t have sourdough, use 1/4 cup plain yogurt mixed with 1/4 tsp baking powder.
2 eggs (room temperature) 🥚
Use: Binds ingredients and adds richness.
Substitutions: Use 2 flax eggs (2 tbsp ground flaxseed + 6 tbsp water) for a vegan option.
1 1/2 cups (320g) sugar 🍬
Use: Sweetens the cake and helps with browning.
Substitutions: Replace with coconut sugar or maple syrup (reduce liquid in recipe by 1/4 cup if using syrup).
1 tsp (5g) vanilla extract 🌸
Use: Enhances flavor with a warm, aromatic note.
Substitutions: Use almond extract or skip if unavailable (though flavor will be less complex).
1/2 cup (125g) vegetable oil 🥄
Use: Keeps the cake moist and tender.
Substitutions: Substitute with melted butter or coconut oil for a different fat profile.
1/3 cup (40g) cocoa powder 🍫
Use: Boosts chocolate intensity in the batter.
Substitutions: Same as above (Dutch-processed or carob powder).
1 1/2 tsp (8g) baking powder 🧁
Use: Helps the cake rise and become fluffy.
Substitutions: Use 1 tsp baking soda plus 1 tsp cream of tartar if baking powder is out.
3/4 tsp (4g) baking soda 🧁
Use: Works with acidic ingredients (like cocoa) for additional leavening.
Substitutions: Can increase baking powder slightly, but adjust for acidity.
3/4 tsp (4g) salt 🧂
Use: Balances sweetness and enhances flavor.
Substitutions: Use sea salt or kosher salt (adjust quantity slightly).
2/3 cup (150g) boiling water 💧
Use: Activates cocoa and coffee, intensifying flavor.
Substitutions: Use hot coffee for an even richer taste (omit instant coffee if doing so).
1 1/2 tsp (8g) instant coffee powder (optional) ☕
Use: Deepens chocolate flavor without a strong coffee taste.
Substitutions: Omit if you don’t have it, or use espresso powder.
1 1/2 tbsp (20g) butter (for greasing) 🧈
Use: Prevents sticking in the pan.
Substitutions: Use cooking spray or coconut oil.

For Chocolate Cake Frosting (Optional):

1 1/3 cups (400g) sweetened condensed milk 🥛
Use: Creates a creamy, sweet base for the frosting.
Substitutions: Use coconut condensed milk for dairy-free, or make a simple ganache with cream and chocolate.
1 cup (170g) milk chocolate pieces 🍫
Use: Adds rich chocolate flavor and smooth texture to the frosting.
Substitutions: Use dark chocolate for a less sweet frosting, or white chocolate for variety.
1 tsp (5g) vanilla extract 🌸
Use: Enhances the frosting’s flavor.
Substitutions: Same as above (almond extract or omit).

Overnight Sourdough Chocolate Cake with Rich Chocolate Frosting

Step-by-Step Guide To The Perfect Sourdough Chocolate Cake

Follow these detailed steps to create your Overnight Sourdough Chocolate Cake, with tips and explanations for each stage to ensure success.

Preparing the Sourdough Base (Overnight Fermentation)

Mix the Initial Dough:
In a large mixing bowl, combine 2 1/4 cups (280g) all-purpose flour, 1 cup (250g) cold milk, 1/4 cup (20g) cocoa powder, and 1/4 cup (50g) sourdough discard or active starter. Use a whisk or spatula to stir until no dry flour remains. The mixture will be thick and slightly sticky.
Tip: Ensure your sourdough discard is at room temperature for better fermentation. If it’s too cold, let it sit out for 30 minutes before mixing.
Why It Matters: This step starts the fermentation process, which not only develops flavor but also breaks down gluten, making the cake easier to digest.
Cover and Ferment:
Cover the bowl tightly with plastic wrap or a clean kitchen towel and let it sit at room temperature for 8-12 hours (overnight works best). Place it in a draft-free area, like your kitchen counter.
Tip: The ideal fermentation temperature is between 70-75°F (21-24°C). If your kitchen is cooler, consider placing the bowl near a warm (not hot) oven.
What to Look For: After fermenting, the mixture should look slightly puffed and have a tangy aroma. This indicates the sourdough has done its magic!

Baking the Cake

Preheat and Prepare the Pan:
Preheat your oven to 350°F (175°C). While it heats, grease a bundt pan thoroughly with 1 1/2 tbsp (20g) butter. Use a pastry brush to ensure every nook and cranny is coated, or sprinkle a bit of flour over the butter for extra non-stick protection.
Tip: A bundt pan creates a stunning shape, but you can use two 8-inch round pans if preferred. Adjust baking time to 35-40 minutes for round pans.
Why It Matters: Proper greasing prevents the cake from sticking and ensures easy removal.
Beat the Wet Ingredients:
In a separate large bowl, crack 2 eggs and add 1 1/2 cups (320g) sugar and 1 tsp (5g) vanilla extract. Use a whisk or electric mixer to beat until the mixture is pale yellow and slightly frothy, about 2-3 minutes. This incorporates air, making the cake lighter.
Tip: Ensure eggs are at room temperature for better volume. If they’re cold, place them in warm water for 10 minutes.
Next, slowly drizzle in 1/2 cup (125g) vegetable oil while mixing. Then, sift in 1/3 cup (40g) cocoa powder, 1 1/2 tsp (8g) baking powder, 3/4 tsp (4g) baking soda, and 3/4 tsp (4g) salt. Mix until smooth and well combined.
Tip: Sifting prevents lumps, especially with cocoa powder, which can clump.
Add Boiling Water and Coffee:
Carefully stir in 2/3 cup (150g) boiling water and 1 1/2 tsp (8g) instant coffee powder (if using). The mixture will thin out significantly, but this is normal—it ensures a moist, fudgy texture.
Tip: Pour the boiling water slowly to avoid splashing, and use a sturdy spatula for mixing. The coffee enhances chocolate flavor without making the cake taste like coffee.
Why It Matters: The heat from the water blooms the cocoa and coffee, unlocking their full flavor potential.
Fold in the Fermented Mixture:
Gently fold the fermented sourdough mixture into the wet ingredients using a spatula. Be careful not to overmix—stop as soon as the batter is uniform. Lumps are okay; they’ll bake out.
Tip: Use a folding motion (scoop from the bottom and fold over) to preserve air bubbles. Overmixing can make the cake dense.
Pour and Bake:
Pour the batter into the prepared bundt pan, spreading it evenly with a spatula. Tap the pan gently on the counter to remove air bubbles. Bake in the preheated oven for 50 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Tip: Check the cake at 45 minutes to avoid overbaking. If the top browns too quickly, tent it with foil.
Why It Matters: Baking time can vary based on oven accuracy, so use the toothpick test as your guide.
Cool the Cake:
Remove the cake from the oven and let it cool in the pan for 15 minutes. Then, invert it onto a wire rack to cool completely, about 1-2 hours. Don’t rush this step—warm cake can crack or stick.
Tip: If the cake sticks, run a thin knife around the edges before inverting.

Making the Chocolate Frosting (Optional)

Heat the Condensed Milk:
In a medium saucepan, warm 1 1/3 cups (400g) sweetened condensed milk over medium heat, stirring constantly. Heat until it’s just warm to the touch (about 5 minutes). Don’t let it boil.
Tip: Use a heavy-bottomed pan to prevent scorching. Stirring prevents the milk from forming a skin.
Melt the Chocolate:
Add 1 cup (170g) milk chocolate pieces and 1 tsp (5g) vanilla extract to the warm condensed milk. Stir continuously until the chocolate melts completely and the mixture is smooth and glossy.
Tip: If the chocolate doesn’t melt easily, remove the pan from heat and let residual warmth do the work. Avoid overheating, as it can cause the frosting to seize.
Cool and Spread:
Remove the frosting from heat and let it cool slightly, about 5-10 minutes. It should thicken but remain pourable. Pour it over the cooled cake, using a spatula to spread it evenly. Let it drip down the sides for a dramatic effect.
Tip: If the frosting sets too quickly, reheat it gently over low heat, stirring until pourable again.
Set the Frosting:
Allow the frosting to set at room temperature for at least 30 minutes before serving. For faster setting, refrigerate the cake for 15 minutes, but bring it back to room temperature before slicing for the best flavor.
Tip: Cover loosely with plastic wrap if setting for longer to prevent a skin from forming.

Topping Suggestions

Elevate your cake with these delicious additions:

Sprinkles: Add colorful sprinkles for a festive touch.
Chopped Nuts: Sprinkle chopped walnuts, pecans, or hazelnuts for crunch.
Sea Salt Flakes: A pinch of flaky sea salt on top enhances the chocolate flavor.
Fresh Berries: Serve with raspberries or strawberries for a fresh contrast.
Whipped Cream: Dollop with homemade whipped cream for extra richness.

How to Store & Reheating

Storage: Store the cake in an airtight container at room temperature for up to 2 days. For longer storage, refrigerate for up to 5 days. If frosted, cover loosely to avoid smudging the topping.
Freezing: Wrap unfrosted cake tightly in plastic wrap and foil, then freeze for up to 3 months. Thaw overnight in the fridge before frosting.
Reheating: Warm individual slices in the microwave for 15-20 seconds to restore moisture. Avoid overheating, as it can melt the frosting. For a crisp edge, toast lightly in a 300°F oven for 5 minutes.

What to Serve With

Pair this rich dessert with:

Coffee or Tea: A hot cup of coffee or herbal tea balances the sweetness.
Ice Cream: Serve with a scoop of vanilla or chocolate ice cream for a molten lava cake vibe.
Fresh Fruit: Sliced strawberries, bananas, or oranges cut through the richness.
Whipped Cream: A light dollop adds a creamy contrast.
Milk: A cold glass of milk is a classic companion for chocolate cake.

FAQs

Why did my chocolate cake sink in the middle?

This could be due to underbaking, overmixing, or opening the oven door too early. Ensure the toothpick test shows clean or slightly moist crumbs, and avoid drafts during baking.

Can I make the chocolate frosting ahead of time?

Yes! Store cooled frosting in an airtight container in the fridge for up to 3 days. Reheat gently over low heat, stirring until pourable.

How do I know if my sourdough is active enough?

It should double in size within 4-6 hours at room temperature. If it’s sluggish, feed it flour and water the day before and let it ferment longer.

Can I use a different pan?

Absolutely. Use two 8-inch round pans (adjust bake time to 35-40 minutes) or a 9×13-inch pan (bake for 45-50 minutes). Grease and flour any pan to prevent sticking.

Why does the sourdough chocolate cake call for boiling water?

Boiling water blooms the cocoa and coffee, intensifying their flavors and ensuring a moist cake. It’s a key step for fudgy texture.

Can I make chocolate cake without sourdough discard?

Yes! Substitute with 1/4 cup plain yogurt mixed with 1/4 tsp baking powder. Skip the overnight fermentation and proceed directly to baking.