Name: Sourdough Vanilla Birthday Cake with Chocolate Cream Cheese Frosting
Prep time: 10 min
Cook time: 40 min
Total time: 50 min
Ingredients: 3 cups all-purpose flour (360g); 1/4 cup cornstarch (30g); 2 tablespoons baking powder (24g); 1/4 teaspoon salt (1.5g); 1 cup salted butter (226g, melted); 2 1/2 cups granulated sugar (500g); 3 large eggs (room temperature); 1/2 cup sour cream (120g, room temperature); 2 teaspoons pure vanilla extract (8g); 2 cups whole milk (480g, room temperature); 1/2 cup sourdough discard (120g, room temperature); 1 cup salted butter (226g, room temperature); 16 ounces full-fat cream cheese (2 blocks) (452g, room temperature); 3/4 cup unsweetened cocoa powder or Dutch-processed cocoa (75g); 1 teaspoon vanilla extract (4g); 6 cups powdered sugar (720g); Sprinkles (optional)

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This sourdough vanilla cake is a two-layered, incredibly moist cake topped with a creamy chocolate cream cheese frosting! Top it with sprinkles for the best birthday cake! Use up the extra sourdough starter you have saved for this cake that’s perfect for any occasion (not just birthdays!).

One slice of a two-layered sourdough vanilla birthday cake with chocolate frosting and sprinkles sits on a plate with a fork.

My favorite cake combination is vanilla cake with chocolate frosting. But I wasn’t sure if I was alone in that. So I polled everyone on social media to ask if they’d rather I frost this cake with chocolate or vanilla frosting.

And honestly? It was pretty close, but chocolate did end up prevailing. If you would rather frost this cake with vanilla frosting, I have a lovely vanilla frosting recipe on my sourdough vanilla cake recipe here (I recommend you double it if you’re making this cake, though!).

This cake is perfect for not only birthdays, but also other celebrations or gatherings. Doctor it up however you’d like. I’ve never been much of a cake decorator, but I do find it fun to practice my skills on a lovely layered cake!

And, the best part is that to save time, you can make the cake part the day ahead of time. Just wrap the cakes in plastic wrap once they’ve cooled to ensure they stay moist. Then you can make the frosting and frost the cake the next day!

The full sourdough vanilla birthday cake with chocolate cream cheese frosting and sprinkles sits on a wooden cake stand. A jar of sourdough discard sits in front of it.

Ingredients

The two main rules to ensuring you have a light, fluffy, and moist cake as opposed to a dense one: use room temperature ingredients *not* cold! And avoid overmixing. Mix all ingredients until they are *just* incorporated!

Cake Ingredients

All-purpose flour – I use unbleached, good-quality flour.
Cornstarch – This helps provide a light, fluffy texture.
Baking powder
Granulated sugar
Salt
Salted butter – I always use salted butter in my baking. You can use unsalted, but add an additional 1/4 teaspoon salt.
Eggs – make sure the eggs are room temperature!
Sour cream – room temperature sour cream is very important to ensure you get a soft, fluffy, light cake!
Vanilla extract
Whole milk – make sure the milk is room temperature here as well. You can substitute other milk if you don’t have whole milk. I just recommend it for the creaminess it provides.
Sourdough discard – let your sourdough discard sit out so it is at room temperature.

Chocolate Cream Cheese Frosting Ingredients

Salted butter – again, if you only have unsalted, add an additional 1/4 teaspoon of salt
Full-fat cream cheese – you will want the block-style cream cheese, not whipped cream cheese.
Unsweetened cocoa powder (or Dutch-processed cocoa)
Vanilla extract
Powdered sugar – sifting the powdered sugar beforehand ensures you don’t get a lumpy frosting!
Sprinkles (optional) – I use Wilton’s dye free sprinkles.

Step-By-Step Instructions

A glass mixing bowl sits with the dry ingredients needed for the sourdough vanilla birthday cake.

Prep Your Pans & Oven

Preheat your oven to 350°F (175°C).

Grease two 9-inch round cake pans and line the bottoms with parchment paper. This ensures the cakes release easily after baking.

Sift the Dry Ingredients

In a large bowl, sift together the flour, cornstarch, and baking powder.

Sifting helps create a lighter, more delicate crumb and prevents clumps in the batter. Set aside.

A glass mixing bowl sits with the wet ingredients needed for the sourdough vanilla birthday cake.

Combine Melted Butter & Sugar

In a separate large mixing bowl, whisk together the melted butter and granulated sugar until smooth and glossy.

Because we’re using melted butter, the mixture will look silky rather than fluffy — that’s exactly what we want.

Add the Eggs, Sour Cream & Vanilla

Add the room temperature eggs, sour cream, and vanilla extract to the butter mixture.

Whisk until fully incorporated and smooth. The batter should look creamy and cohesive at this stage.

The sourdough vanilla birthday cake batter is split evenly between two 9 inch round cake pans.

Alternate Dry Ingredients & Milk

Now we’ll alternate the dry ingredients and milk for a smooth, evenly mixed batter.

Add half of the dry ingredients and gently mix.
Pour in half of the milk and mix again.
Repeat with the remaining dry ingredients.
Add the remaining milk and mix just until combined.

Be careful not to overmix — this keeps the cake soft and tender.

Fold in the Sourdough Discard

Add the room temperature sourdough discard and gently fold it in until just incorporated.

The batter should be smooth and pourable. Avoid overworking it.

Bake

Divide the batter evenly between your prepared cake pans.

Bake for about 40 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cakes to cool in the pans for 10–15 minutes before transferring them to a wire rack to cool completely.

The cakes must be fully cooled before frosting.

A glass mixing bowl sits with the creamy chocolate cream cheese frosting.

Beat Butter & Cream Cheese

In a large bowl, beat the room temperature butter and cream cheese together until smooth and creamy. There should be no lumps.

Add Cocoa & Vanilla

Add the cocoa powder and vanilla extract. Mix until fully combined and smooth.

Add Powdered Sugar

Gradually add the powdered sugar, one cup at a time, beating until the frosting is thick, smooth, and fluffy.

If needed, adjust the consistency by adding a small splash of milk to thin or extra powdered sugar to thicken.

Layer & Frost

Place one cake layer on a serving plate or cake stand.

Spread an even layer of frosting over the top.

Place the second cake layer on top and frost the top and sides of the cake until smooth.

The sourdough vanilla birthday cake sits on a wooden cake stand. Two slices have been taken out and each sits on a floral plate with forks.

Decorate

Finish with sprinkles if desired for that classic birthday cake look. Slice, serve, and enjoy!!

A slice of fluffy sourdough vanilla birthday cake sits on a floral plate. It is topped with chocolate cream cheese frosting.

Helpful Tips for the BEST Cake

Use fully room temperature ingredients. Eggs, sour cream, milk, and sourdough discard should not be cold. Room temperature ingredients blend more smoothly and create a lighter, more even crumb.
Sift your dry ingredients. This step prevents clumps and keeps the cake soft and tender. It also evenly distributes the baking powder for consistent rise.
Don’t overmix the batter. Mix just until combined after each addition. Overmixing develops gluten and can make the cake dense instead of fluffy.
Alternate dry ingredients and milk properly. Adding them in stages keeps the batter smooth and prevents curdling or overworking.
Scrape down the bowl. Use a rubber spatula to scrape the sides and bottom of the bowl so everything is fully incorporated without extra mixing.
Weigh your ingredients if possible. Using grams ensures consistent, bakery-style results every time.
Check for doneness early. Ovens vary. Start checking around 35 minutes. The cake is done when a toothpick inserted in the center comes out clean or with a few moist crumbs.
Cool completely before frosting. Even slightly warm cakes will melt the frosting and cause slipping layers.
Level your cake layers if needed. If the cakes dome slightly, trim the tops with a serrated knife for clean, even stacking.
Chill briefly before slicing. Refrigerating the frosted cake for 20–30 minutes helps the frosting set and makes slicing cleaner.

Equipment

Two 9-inch round cake pans
Parchment paper
Large mixing bowls
Whisk
Rubber spatula
Fine mesh sieve (for sifting dry ingredients)
Electric hand mixer or stand mixer
Measuring cups and spoons
Kitchen scale (optional, for accuracy)
Cooling rack
Offset spatula or butter knife (for frosting)
Cake stand or serving plate
Piping bag
Piping tip (I used the Wilton 1M)

Storage

Refrigerator:
Store the cake covered in an airtight container or cake dome in the refrigerator for up to 4 days.

For best texture and flavor, allow the cake to sit at room temperature for 30–60 minutes before serving. This softens the butter in the cake and frosting.

Freezer:
The unfrosted cake layers can be wrapped tightly in plastic wrap and then foil and frozen for up to 2 months. Thaw overnight in the refrigerator before frosting.

Make Ahead Instructions

Bake the Cake Layers in Advance:
Bake the cake layers up to 2 days ahead. Once completely cooled, wrap tightly in plastic wrap and store at room temperature (if frosting within 24 hours) or refrigerate.
Freeze for Longer Storage:
Wrap cooled layers tightly and freeze for up to 2 months. Assemble and frost once fully thawed.
Prepare the Frosting Ahead of Time:
The chocolate cream cheese frosting can be made 1–2 days in advance and stored in an airtight container in the refrigerator. Before using, let it come to room temperature and re-whip until smooth and fluffy.
Fully Assemble in Advance:
You can frost the entire cake up to 24 hours before serving. Store in the refrigerator, then bring to room temperature before slicing for the best texture.