Three-layer chocolate birthday cake with peanut butter frosting, garnished with Reese's Peanut Butter Cups and glossy chocolate ganache, set on a silver cake stand against a dark marble background with warm lighting and soft bokeh.

Decadent Peanut Butter Cup Birthday Cake: A Chocolate Lover’s Dream

Decadent Peanut Butter Cup Birthday Cake: A Chocolate Lover’s Dream

Quick & Easy Chocolate Peanut Butter Celebration Cake

Key Information
  • Prep Time: 30 minutes
  • Cook Time: 40 minutes
  • Total Time: 1 hour 10 minutes
  • Servings: 12 slices
  • Difficulty: Moderate
  • Dietary Tags: Vegetarian, Contains Allergens
Equipment Needed
Ingredients
Cake Base
  • 1 box Devil’s food cake mix
  • 4 large eggs
  • 1 cup buttermilk
  • 2 sticks (1 cup) unsalted butter, room temperature
  • 1/2 cup vegetable oil
  • 2 tsp vanilla extract
  • 20-30 mini Reese’s Peanut Butter Cups, chopped
Peanut Butter Frosting
  • 1 1/2 cups creamy peanut butter
  • 1 cup unsalted butter, softened
  • 4 cups powdered sugar
  • 1/4 cup milk
  • 1 tsp vanilla extract
Optional Garnishes
  • Extra chopped Peanut Butter Cups
  • Chocolate syrup
  • Sprinkles
Method
Cake Preparation
  1. Preheat oven to 350°F. Grease your baking pan thoroughly.
  2. In a large mixing bowl, combine:
    • Cake mix
    • Eggs
    • Buttermilk
    • Softened butter
    • Vegetable oil
    • Vanilla extract
  3. Mix on medium speed until smooth and well combined, about 2-3 minutes.
  4. Fold in half of the chopped Peanut Butter Cups.
  5. Pour batter into prepared pan. Sprinkle remaining Peanut Butter Cups on top.

Close-up of hands mixing chocolate cake batter with chunks of Reese's Peanut Butter Cups in a glossy white bowl, surrounded by ingredients on a marble countertop.

Baking
  1. Bake for 35-40 minutes. Check doneness with a toothpick – it should come out with just a few moist crumbs.
Frosting
  1. While cake cools, prepare frosting:
    • Cream butter and peanut butter until smooth
    • Gradually add powdered sugar
    • Mix in milk and vanilla
    • Beat until light and fluffy
  2. Once cake is completely cool, frost generously.
  3. Decorate with extra Peanut Butter Cups, chocolate drizzle, and sprinkles.

Overhead view of a decadent chocolate layer cake on a silver stand, topped with creamy peanut butter frosting, halved Reese's Cups, chocolate syrup drizzle, and gold sprinkles against a dark background, illuminated by dramatic side lighting.

Pro Tips
  • Room temperature ingredients create a smoother batter
  • Don’t overmix – this can make the cake tough
  • Let cake cool completely before frosting
Storage
  • Counter: 2 days in covered container
  • Refrigerator: Up to 5 days
  • Freezer: Unfrosted layers up to 3 months
Variations
  • Cupcake Version: Bake in muffin tins, 18-22 minutes
  • Gluten-Free: Use gluten-free cake mix
  • Vegan: Substitute with plant-based alternatives
Common Mistakes to Avoid
  • Using natural peanut butter (can separate)
  • Frosting a warm cake (causes melting)
  • Overmixing batter
Nutritional Note

Approximately 415 calories per slice. High in sugar and fat, moderate protein from peanut butter.

Allergen Warning: Contains peanuts, wheat, eggs, dairy

Enjoy this show-stopping birthday cake that’s sure to make any chocolate and peanut butter lover’s day!

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