Special equipment: a 12-by-2-inch heart-shaped cake pan; one 24-count or two 12-count mini muffin tins; 24 brown or black mini cupcake liners; one 16-inch round cardboard cake board
Spray a 12-by-2-inch heart-shaped cake pan with nonstick spray. Use the pan to trace a heart onto a piece of parchment. Cut out the heart and line the bottom of the pan with it.
Prepare one of the cake mixes according to the package instructions. Pour the cake batter into the prepared cake pan and bake according to the package instructions for a 9-by-13-inch pan or until a toothpick inserted in the center comes out clean. Let cool, then remove from the pan.
Line two 12-cup (or one 24-cup) mini cupcake tins with brown or black mini cupcake liners. Prepare the second cake mix according to the package instruction. Add about 1 tablespoon of batter to each cupcake liner. Bake until a cake tester inserted in the center comes out clean, 5 to 8 minutes. Let cool, then remove the cupcakes from the tins. Use any leftover batter to make more cupcakes.
Melt the white chocolate in a double boiler. Set aside.
Using a serrated knife, slice off the domed top of the heart cake to create a flat even surface. You want the final height of the cake to be about 1 inch. Save any cake scraps to make cake pops. Place a 16-inch round cake board on top of the cake and flip upside down so the parchment paper is on top. Carefully remove the parchment paper and discard. Cut some strips of parchment paper and slide them under the cake a little bit to cover the cake board; this will help keep the cake board clean when you frost the cakes. Set the cake aside.
Carefully dip the top of 16 mini cupcakes into the Chocolate Ganache to cover each cupcake to the paper liner. Carefully dip the tops of the remaining 8 mini cupcakes into the melted white chocolate. Let set for about 5 minutes.
For the 16 ganache-coated cupcakes: Top 3 with 3 chocolate-covered espresso beans and 3 with white chocolate shavings; drizzle 3 with melted white chocolate; dip 4 in the cocoa powder and top 3 with red heart sprinkles. For the 8 white chocolate-topped cupcakes: Top 4 with pink heart sprinkles and 4 with a pinch of chopped pistachios. Feel free to mix it up and do any combination of these decorations.
Frost the entire cake with the red frosting. Remove the parchment paper strips and discard. Cut the icing sheet into 1 1/2-inch-wide strips to go around the heart cake; the strips should come up about 1/2 inch above the surface of the cake. You will need 4 strips to make it around the entire heart cake; the fourth strip will need to be shorter, so cut it to fit cleanly between the end of the first and third strips. Carefully press the icing strips around the cake to form the rim of the box. Arrange the cupcake "candies" inside the box on top of the cake.
In a small pot, bring the cream to a simmer.
Put the chocolate chips in a small bowl. Pour over the hot cream and let stand for 2 minutes. Wish until blended and smooth. Whisk in the corn syrup. Let stand before using until the consistency is similar to pancake batter.