Make the Cupcakes

1. Preheat oven to 350°F and line a muffin tin with cupcake liners.
2. In a large bowl, combine cake mix, pudding mix, milk, oil, eggs plus extra yolk, sour cream, vanilla, and espresso powder.
3. Mix until smooth and thick. The batter should look creamy and rich.
4. Fill liners about 2/3 full.
5. Bake for 18 to 22 minutes, until a toothpick inserted in the center comes out with a few soft crumbs.
6. Let the cupcakes cool completely.

Make the Frosting

1. Beat the butter until smooth and fluffy.
2. Add powdered sugar and cocoa powder, mixing until combined.
3. Add heavy cream and vanilla, then beat until light, creamy, and easy to pipe. Adjust cream as needed.

Assemble

1. Remove the center of each cupcake. You can use a cupcake corer if you have one. 
2. Fill with Nutella and place the top piece back on.
3. Pipe or spread chocolate buttercream onto each cupcake.
4. Finish with sanding sugar, pearl sprinkles, and a Dove heart chocolate.