Truffle Box Cake

To make the cakes: Heat oven to 350 degrees F. Lightly coat four cups of a muffin tin and the two heart-shaped cake pans with cooking spray. Line the bottoms of the hearts with parchment paper; coat the paper. In a medium bowl, whisk together the flour, baking powder, and salt.

Using an electric mixer, beat the granulated sugar, vanilla, and 8 tablespoons (1 stick) butter in a large bowl until light and fluffy, about 3 minutes. Beat in the eggs, one at a time. Reduce the mixer speed to low and alternately add the flour mixture and 4 tablespoons milk, mixing just until incorporated.

Spread 3/4 cup batter into each heart pan. Divide the remaining batter among the muffin cups (about 1/4 cup each). Bake until a wooden pick inserted in the center comes out clean, 18 to 22 minutes. Let cool in the pans for 10 minutes before transferring to a wire rack to cool completely (cool the hearts upside down).

Using an electric mixer, beat the confectioners' sugar, 2 teaspoons milk and the remaining 6 tablespoons butter in a large bowl until light and fluffy, about 3 minutes. Transfer 1/4 cup frosting to a small bowl. Add the cocoa powder and remaining 1 tablespoon milk to the remaining frosting and beat to combine.

To make the cake ball truffles: Working over a large bowl, crumble the cupcakes into fine crumbs. Add the 1/4 cup reserved white frosting and mix until evenly distributed. Shape level teaspoons of mixture into balls and place on a parchment-lined baking sheet. Freeze for at least 1 hour and up to overnight. Melt the chocolate according to package directions. Dip the balls in chocolate, tapping off extra. Decorate as desired (sprinkle with nonpareils, flaked salt, or chopped nuts when wet, or drizzle with melted chocolate when set). Return to the prepared baking sheet and let set, about 30 minutes.