Step 1

Preheat the oven to 350 degrees F. Spray a 9-inch round cake pan with cooking spray.

Step 2

Combine the flour, cocoa powder, sugar, baking soda, baking powder and salt in a large bowl. Add the egg, egg yolk, sour cream, oil, vanilla and 1/2 cup hot water and whisk until combined. Pour the batter into the prepared cake pan. Scatter the sliced strawberries on top and gently press them into the batter.

Step 3

Bake until a tester inserted in the center of the cake comes out clean, 55 to 60 minutes. Transfer to a wire rack and cool for 30 minutes.

Step 4

Run a knife around the edge of the cake and invert onto a wire rack. Flip the cake back over and let cool completely, about 1 hour.

Step 5

Once the cake has cooled, put the semisweet chocolate and the white chocolate in separate small microwave-safe bowls. Microwave the semisweet chocolate in 30-second intervals, stirring well with a rubber spatula between each, until completely melted and smooth, about 1 minute. Drizzle the cake with the melted chocolate. Repeat the melting and drizzling process with the white chocolate.

Step 6

Garnish the top edge of the cake with the whipped cream. Cut the remaining 5 whole strawberries in half lengthwise and place the pieces cut-side down around the edge of the cake.