Preheat Oven: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

Make the Cake Batter:

In a large mixing bowl, cream together the softened butter and creamy peanut butter until smooth.

Add the granulated sugar and brown sugar, and beat until light and fluffy.

Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.

In a separate bowl, whisk together the flour, baking powder, and salt.

Gradually add the dry ingredients to the peanut butter mixture, alternating with the milk, beginning and ending with the dry ingredients. Mix until just combined.

Bake the Cake:

Divide the batter evenly between the prepared cake pans.

Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center of the cakes comes out clean.

Allow the cakes to cool in the pans for 10 minutes, then remove from the pans and transfer to a wire rack to cool completely.

Prepare the Frosting:

In a large mixing bowl, beat the softened butter and creamy peanut butter until smooth.

Gradually add the powdered sugar, one cup at a time, mixing well after each addition.

Add the milk and vanilla extract, and continue to beat until the frosting is light and fluffy. If the frosting is too thick, add more milk, a tablespoon at a time, until you reach your desired consistency.

Assemble the Cake:

Place one cake layer on a serving plate and spread a generous amount of frosting on top.

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

Decorate with chopped peanuts or a drizzle of melted chocolate, if desired.