12 TBS (1 1/2 sticks) unsalted butter, at room temperature
2/3 cup sugar
2/3 cup light brown sugar, packed
2 extra-large eggs, at room temperature
2 tsp. vanilla
1 cup buttermilk, shaken, at room temperature
1/2 cup sour cream, at room temperature
2 TBS brewed coffee
1 3/4 cups flour
1 cup cocoa powder
1 1/2 tsp. baking soda
1/2 tsp. kosher salt
1 1/2 cups powdered sugar, sifted
1 1/2 cups creamy peanut butter
8 TBS (1 stick) unsalted butter, at room temperature
1 tsp. vanilla
3/8 tsp. kosher salt
1/3 cup + 3 TBS heavy cream
Preheat oven to 350. Line bottoms of two 8-inch cake pans with waxed paper. Grease and lightly flour the waxed paper.
Using an electric mixer, cream the butter and two sugars on high speed until light and fluffy, about 5 minutes. Lower the speed to medium, add the eggs one at a time, then add the vanilla and mix well. In a separate bowl, whisk together the buttermilk, sour cream and coffee. In another bowl, sift together the flour, cocoa, baking soda and salt. On low speed, add the buttermilk mixture and the flour mixture alternately in thirds to the mixer bowl, beginning with the buttermilk mixture and ending with the flour mixture. Mix only until blended. Fold the batter with a rubber spatula to make sure it is completely blended.
Divide the batter between the two cake pans. Bake in the middle of the oven for 30-35 minutes, until a toothpick comes out clean. Cool for 10 minutes on a wire rack, remove from pans, and allow to cool completely before frosting.
Combine powdered sugar, peanut butter, butter, vanilla and salt in a mixing bowl. Mix on medium-low speed until creamy. Add the cream and beat on high speed until the mixture is light and smooth.
Source: Barefoot Contessa At Home - Ina Garten