01 -
Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
02 -
In a medium bowl, whisk together all-purpose flour, baking powder, baking soda, and salt until evenly mixed.
03 -
In a large bowl, beat unsalted butter and creamy peanut butter until smooth and creamy using an electric mixer.
04 -
Gradually add granulated sugar, beating until light and fluffy. Add eggs one at a time, mixing well after each addition. Blend in vanilla extract.
05 -
Alternately add flour mixture and buttermilk to the peanut butter mixture, beginning and ending with the dry ingredients. Mix until just incorporated without overmixing.
06 -
Gently fold in the M&M's with a spatula, distributing them evenly through the batter.
07 -
Divide batter equally between prepared pans. Bake for 25–30 minutes or until a toothpick inserted into the center comes out clean.
08 -
Allow cakes to cool in pans for 10 minutes. Run a knife around the edges, then transfer to a wire rack to cool completely.
09 -
In a large bowl, beat unsalted butter and peanut butter until creamy. Gradually add powdered sugar and continue mixing until smooth. Add heavy cream and vanilla extract, beating until the frosting is light and fluffy.
10 -
Spread frosting over the top of one cake layer. Place second layer on top and coat top and sides evenly with frosting.
11 -
Sprinkle additional M&M's over the finished cake for decoration.