For the Cake:
6 oz best-quality unsweetened chocolate, coarsely shopped
2/3 cup vegetable or canola oil
2 2/3 cup sugar
1 2/3 cup all-purpose flour
1/3 cup best-quality unsweetened cocoa powder
1 tsp baking soda
¾ tsp kosher salt
2/3 cup sour cream
3 large eggs
1 1/3 cups hot strong brewed coffee (I just used hot water)
For the Peanut Butter Frosting:
1 pound confectioner’s sugar, sifted
1 ½ pounds unsalted butter, softened
2 tsp pure vanilla extract
3 Tbsp whole milk
½ cup smooth peanut butter, at room temperature
Position a rack in the center of your oven. Preheat the oven to 350. Butter and flour two 9×2-inch round cake pans, Line each pan with a 9-inch round of parchment paper.
To Make the Cake
1. In the top of a double boiler set over simmering, not boiling, water, melt the chocolate, stirring occasionally. When the chocolate is completely melted, whicsk in the vegetableoil until smooth. Remove from the heat, but keep warm over the hot water.
2. In the bowl, of an electric mixer fitted with the paddle attachment, combine the sugar, flour, cocoa powder, baking soda, and salt, and mix well.
3. In a separate bowl, whisk together the sour cream and eggs until smooth.
4. Add the egg mixture to the flour mixture, and mix until combined. Be sure to scrape down the sides of the bowl. Add the melted chocolate mixture and mix until combined. add the hot coffee (or water) in a stream, and mix until combined. (Again, scrape down the sides and bottom of the bowl.) The batter will be loose.
5. Divide the batter evenly between the prepared cake pans. Bake for 35 to 40 minutes, or until a wooden skewer inserted into the center comes out clean. Remove to a wire rack to cool in the pans for 25 minutes before turning out the layers onto the rack. Cool completely before finishing.
The baked layers may be stored tightly wrapped in plastic wrap at room temperature for 2 days. For longer storage, wrap tightly in plastic wrap and refrigerate for up to 5 days, or freeze wrapped in plastic wrap and them aluminum foil for up to 2 weeks. Do not unwrap before thawing.
To Make the Frosting
1. In the bowl of an electric mixer fitted with the paddle attachment, combine the confectioner’s sugar, butter, vanilla, and milk, and beat until light and fluffy, 2 to 3 minutes.
2. Add the peanut butter and mix until combined. Use the frosting immediately, if possible. It may be stored in an airtight container at room temperature overnight, or in the refrigerator for up to 4 days. Let the frosting come to room temperature and briefly rebeat it in the mixer before using.