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Peanut Butter Cookie Cake

5 from 5 votes
Prep Time 10 minutes
Cook Time 55 minutes
Total Time 1 hour 5 minutes
Servings 18 slices
Calories 439
The best peanut butter blondie, baked to be cut like cake, and topped with decadent chocolate fudge frosting.


Peanut Butter Cookie Cake:

  • 113 grams unsalted butter (8 Tablespoons or ½ cup)
  • 220 grams light brown sugar (1 cup)
  • 150 grams sugar (¾ cup)
  • 3 eggs, refrigerator cold, beaten
  • 192 grams peanut butter (¾ cup)
  • 2 teaspoons vanilla
  • 210 grams all purpose flour (1¾ cup)
  • ¼ teaspoons baking soda
  • ¼ teaspoons baking powder
  • ¾ teaspoons salt
  • 339 grams Reese’s Pieces, Peanut Butter M&Ms, chocolate chips, peanut butter chips, or any combination of them (1½ cups)

Chocolate Fudge Frosting:

  • 53 grams Dutch process cocoa (½ cup plus 2 Tablespoons)
  • 227 grams confectioner’s sugar (2 cups)
  • teaspoon salt
  • 37 grams hot milk
  • teaspoons vanilla extract
  • 113 grams unsalted butter, at room temperature (8 Tablespoons or ½ cup)


  • Preheat oven to 350° F. Line an 9 inch springform baking pan with parchment paper.
  • In a 2-3 quart saucepan, melt the butter over low heat. Remove from heat and allow to cool to room temperature.
  • Mix in sugar and brown sugar. Stir in beaten eggs.
  • Mix in peanut butter and vanilla.
  • Mix in flour, baking soda and baking powder, just until fully incorporated and no flour is visible.
  • Stir in any mix-ins just until incorporated. Spread batter into prepared pan.
  • Bake for 50-55 minutes. The cookie cake is done when the edges are browned and a toothpick inserted in the middle comes out clean. Allow the cookie cake to cool completely in the pan. The middle will sink as it cools.
  • Frosting. In a bowl of an electric mixer (or bowl with a hand mixer), mix the cocoa powder, half the confectioner’s sugar and salt. Stir in the hot milk and the vanilla. Add the butter and rest of the confectioner’s sugar, beating until light and fluffy, approximately 2-3 minutes.
  • Assembly. Slide a metal spatula around the inside edge of the baking pan to loosen the blondie cake from the sides. Release the side portion of the springform pan. Using a spatula, lift the cookie cake onto a serving plate. Spread the frosting over the sunken part of the cookie cake.


  • You can use frozen, cold, or room temperature butter since you are melting it under the lowest heat possilbe anyway.
  • For a flaky top, mix in the sugars immediately after removing the butter from the heat, once it is melted. The heat from the butter will dissolve most of the sugar, which will help create a flaky top.
  • Make sure to allow the cookie cake to cool completely before removing it from the pan and frosting it.
Calories: 439kcal
Course: Dessert, Snack
Cuisine: American
Keyword: Blondies, frosting, M&Ms, peanut butter, reese's pieces


Calories: 439kcal | Carbohydrates: 59g | Protein: 6g | Fat: 21g | Saturated Fat: 11g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 6g | Trans Fat: 1g | Cholesterol: 57mg | Sodium: 198mg | Potassium: 161mg | Fiber: 2g | Sugar: 46g | Vitamin A: 399IU | Vitamin C: 1mg | Calcium: 56mg | Iron: 2mg