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

Sourdough Vanilla Birthday Cake with Chocolate Cream Cheese Frosting

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!).
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Course: Cake, Dessert
Cuisine: American
Prep Time: 10 minutes
Cook Time: 40 minutes
Total Time: 50 minutes
Servings: 16 servings
Author: Jamie

Ingredients

For the Sourdough Vanilla Cake

  • 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

For the Chocolate Cream Cheese Frosting

  • 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

Instructions

Step 1: Prepare the Cake Pans

  • Preheat oven to 350°F (175°C).
  • Grease two 9-inch round cake pans and line the bottoms with parchment paper for easy release.

Step 2: Sift the Dry Ingredients

  • In a large bowl, sift together: all-purpose flour, cornstarch, baking powder, and salt. Set aside

Step 3: Cream the Butter and Sugar

  • In a separate large mixing bowl, use a whisk or rubber spatula to combine the melted butter and granulated sugar until smooth and well incorporated.
  • Add: eggs, sour cream, vanilla extract.
  • Mix until fully combined and smooth.

Step 4: Alternate Dry Ingredients and Milk

  • Add half of the dry ingredients to the wet mixture and gently mix.
  • Pour in half of the milk and mix again.
  • Repeat with the remaining dry ingredients and the remaining milk, mixing gently between additions.
  • Fold in the sourdough discard last.
  • Mix until just combined.
  • Do not overmix — this ensures a soft, tender crumb.

Step 5: Bake

  • Divide the batter evenly between the prepared pans.
  • Bake for approximately 40 minutes, or until a toothpick inserted into the center comes out clean.
  • Allow cakes to cool in the pans for 10–15 minutes before transferring to a wire rack to cool completely.

Chocolate Cream Cheese Frosting

  • Once the cakes are completely cool, prepare the frosting.
  • In a large bowl, with a hand mixer beat together: butter and cream cheese until smooth and creamy. Add: cocoa powder, vanilla extract, Mix until combined
  • Gradually add powdered sugar, one cup at a time, beating until smooth and fluffy.
  • If needed, adjust consistency by adding a tablespoon of milk (to thin) or additional powdered sugar (to thicken).

Assemble the Cake

  • Place one cake layer on a serving plate.
  • Spread an even layer of frosting over the top.
  • Add the second cake layer and frost the top and sides of the cake.
  • Finish with sprinkles, if desired.

Notes

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.

Nutrition

Serving: 1serving | Calories: 756kcal | Carbohydrates: 103g | Protein: 8g | Fat: 37g | Saturated Fat: 22g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 10g | Trans Fat: 1g | Cholesterol: 132mg | Sodium: 497mg | Potassium: 201mg | Fiber: 2g | Sugar: 78g | Vitamin A: 1235IU | Vitamin C: 0.1mg | Calcium: 182mg | Iron: 2mg
Calories: 756kcal
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