chocolate-berry ice cream cake

the goods:

1/4 cup unsweetened cocoa powder

1/2 cup all-purpose flour

1/2 cup sugar

1/2 teaspoon baking soda

1/4 teaspoon baking powder

1/4 teaspoon salt

1 large egg yolk

1/4 cup buttermilk

1 tablespoon vegetable oil

1/2 teaspoon vanilla extract

1 cup fresh or thawed frozen blackberries (5 ounces)

1 pint vanilla ice cream, softened

1 pint raspberry sorbet, softened

Preheat oven to 350 degrees, Lightly coat an 8-inch springform cake pan with cooking spray. In a large bowl, whisk together cocoa powder, flour, sugar, baking soda, baking powder, and salt. Whisk in egg yolk, buttermilk, 1/4 cup warm water, oil, and vanilla. Pour batter into pan and bake until cake pulls away from sides and toothpick inserted in center comes out clean, about 15 minutes. Let cool completely in pan on wire rack, 1 and 1/2 hours.

Cut one or two pieces parchment paper 1 inch taller than pan side and place between cake and inside of pan, overlapping if necessary (parchment should fit snugly around entire circumference of cake).

Place blackberries in a medium bowl and lightly mash with a fork. Stir in vanilla ice cream. Working quickly, spread ice cream mixture in an even layer over cooled cake. Freeze until ice cream is very firm, 2 hours. In a small bowl, stir sorbet until spreadable. Spread in an even layer over ice cream and freeze until set, 1 hour.

To serve, unmold cake and peel away parchment.