6ouncesgood-quality semisweet chocolatebroken into small pieces
6tbspunsalted butter
2 1/2cupsconfectioners' sugar
1tablespoonlight corn syrup
1/2cupsour cream
1teaspoongood-quality vanilla extract
Instructions
Take everything out of the refrigerator so that all ingredients can come room temperature.
Preheat the oven to 350 degrees F.
Put all the cake ingredients: flour, sugar, baking powder and soda, cocoa, butter, eggs, vanilla, and sour cream into a food processor and process until you have a smooth, thick batter.
Divide this batter, using a rubber spatula to help you scrape and spread, into the prepared tins and bake until a cake tester comes out clean, 22-25 minutes. Remove the cakes, in their tins, to a wire rack and let cool for 10 minutes before turning out of their tins.
To make the frosting, melt the chocolate and butter in a good-sized bowl either in the microwave or suspended over a pan of simmering water. Cool.
Place confectioners' sugar into the food processor and blitz to remove lumps. Add remaining frosting ingredients and process until smooth.
Spoon about 1/3 of the frosting onto the center of the cake-half and spread with a knife or spatula until you cover the top of it evenly, leaving about 1/2" from the edges. Sit the other cake on top, normal way up, pressing gently to sandwich the 2 together.
Spoon another 1/3 of the frosting onto the top of the cake and spread it in a swirly, textured way. Spread the sides of the cake last of the icing.