All-in-One Chocolate Cake

This is the perfect chocolate cake: beautiful, melting, intense but not heavy. The batter comes together quickly in a food processor, and the cake bakes at 350 degrees for a while, giving the baker time to assemble the frosting, which is given a luscious sheen by a bit of corn syrup. Use the best chocolate you can find for the frosting, and gild it however you like: with a few flowers, some birthday candles or nothing at all.

INGREDIENTS

• Butter for greasing baking pans
• 1½cups all-purpose flour
• 1cup sugar
• 1teaspoon baking powder
• ½teaspoon baking soda
• ⅓cup best-quality cocoa powder
• 6ounces (1½ sticks) unsalted butter, at room temperature
• 2large eggs, at room temperature
• 2teaspoons vanilla
• ¾cup sour cream, at room temperature
• 6ounces good-quality semisweet chocolate, broken into small pieces
• 3ounces ( ¾ stick) unsalted butter
• 1tablespoon light corn syrup
• ½cup sour cream
• 1teaspoon vanilla
• 2½cups confectioners’ sugar, sifted

PREPARATION

1. Step 1For cake: heat oven to 350 degrees. Butter sides of two 8-inch cake pans, and line bottoms with parchment paper. In the bowl of a food processor fitted with a knife blade, combine flour, sugar, baking powder, baking soda, cocoa powder, butter, eggs, vanilla and sour cream. Process to make a smooth, thick batter.
2. Step 2Using a rubber spatula, divide batter between pans, and smooth tops. Bake until a cake tester inserted in center comes out clean, 25 to 35 minutes; do not overbake. Transfer to a wire rack to cool for 10 minutes before removing from cake pans.
3. Step 3For frosting: Combine chocolate and butter in a large heat-proof bowl, and heat until melted in a microwave oven or over a pan of simmering water. Remove from heat, and allow to cool for 5 minutes. Stir in corn syrup, sour cream, and vanilla. Whisk in confectioners’ sugar until very smooth. Frosting should be thick and spreadable. If necessary, add a teaspoon or two of boiling water to thin it, or additional sifted confectioners’ sugar to thicken.
4. Step 4Cut four strips of waxed or parchment paper, and place them side by side on a cake plate, covering the surface. Place one cake layer domed-side down on plate.
5. Step 5Spoon about a third of the frosting onto center of cake, and use a knife or a spatula to spread it evenly. Place the other cake on top, domed side up. Spoon another third of frosting on top of cake, spreading to make swirls or a smooth finish. Spread sides of cake with remaining frosting, and allow to sit for a few minutes until set. Carefully remove paper strips. Place cake under glass or in an airtight container, and set aside in a cool place until serving.