1. Preheat the oven to 350°F and line a muffin pan with cupcake liners. To create a heart shape, place a small marble or a tightly rolled piece of foil between the pan and each liner on one side.

2. In a large bowl, whisk together the flour, cocoa powder, sugar, baking powder, baking soda, and salt until evenly combined.

3. Add the eggs, milk, vegetable oil, and vanilla extract. Mix until smooth.

4. Slowly pour in the hot coffee or hot water and stir gently. The batter will be thin.

5. Divide the batter evenly among the cupcake liners, filling each about two-thirds full.

6. Bake for 18 to 22 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.

7. Let the cupcakes cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.

8. In a separate bowl, beat the softened butter until creamy. Add the powdered sugar, cocoa powder, heavy cream, and vanilla extract, then beat until the frosting is fluffy and smooth.

9. Pipe or spread the frosting onto the cooled cupcakes, following the heart shape if desired.

10. Finish with pink sprinkles or freeze-dried strawberry pieces before serving.