3/4 cup unsweeteneded cocoa powder, preferably Dutch process
2 teaspoons baking soda
1 teaspoon salt
1 cup neutral vegetable oil such as canola
1 cup sour cream
1 1/2 cups water
2 tablespoons white vinegar
1 teaspoon vanilla
2 -- eggs
10 ounces cream cheese at room temperature
4 ounces unsalted butter at room temperature
5 cups confectioners' sugar sifted
2/3 cup smooth peanut butter (commercial brand so oil doesn't separate)
8 ounces semisweet chocolate coarsely chopped
3 tablespoons smooth peanut butter
2 tablespoons light corn syrup
1/2 cup half-and-half
1/2 cup coarsely chopped peanut brittle or chocolate covered peanuts (optional)
Preheat oven to 350 degrees F. Butter bottoms and sides of three 8-inch round cake pans. Line the bottom with a round of parchment or waxed paper and butter the paper
Sift the flour, sugar, cocoa powder, baking soda and salt into a large bowl. Whisk to combine well.
Add oil and sour cream and blend.
Gradually beat in water and then blend in vinegar and vanilla.
Add eggs and beat until well blended. Scrape down the sides of the bowl and be sure batter is well mixed.
Divide into prepared cake pans.
Bake for 30 – 35 minutes or until toothpick inserted in center comes out almost clean.
Let cool in the pans for 20 minutes. Then invert onto wire racks, carefully peel off the paper lines and let cool completely.
Make frosting: In a large bowl beat cream cheese and butter until light and fluffy. Gradually add confectioners' sugar, 1 cup at a time, mixing thoroughly after each addition and scraping down the sides of the bowl often. Continue to beat on medium speed until light and fluffy 3 – 4 minutes.
Add the peanut butter and beat until thorougly blended.
Frost the cake: place one layer, flat side up on a cake stand or large serving plate. Spread 2/3 cup of the frosting evenly over the top. Repeat with the next layer. Place the last layer on top and frost the top and sides of the cake with the remaining frosting. If cakes seem too soft to easily frost, you can put them in the freezer for 30 minutes to firm up. You could also do a crumb coat first, which is a very thin layer of frosting that binds the crumbs to the frosting.
Chill the cake for another 30 minutes while making the ganache/glaze. This will help the glaze set up faster when poured on the cake.
Make the glaze: combine chocolate, peanut butter and corn syrup in the top of a double boiler or a bowlset over simmering water. Cook, whisking often, until the chocolate is melted and the mixture is smooth.
Remove from heat and whisk in the half-and-half, beating until smooth. Let cool slightly.
Put the cake plate over a large baking sheet to catch drips, pour the warm glaze over the top of the cake. Using an off-set spatula, spread it evenly over the top just to the edges, so that it runs down the sides of the cake in long drips.
Refrigerate, uncovered, for at least 30 minutes to allow the glaze and frosting to set completely.
Remove about 30 minutes to one hour before serving – in hot weather, serve straight from fridge.
Decorate with coarsely chopped peanut brittel (optional)