1. Preheat the oven to 350°F and line a 12-count muffin pan with cupcake liners.

2. In a large bowl, whisk together the flour, cocoa powder, granulated sugar, brown sugar, baking powder, baking soda, and salt.

3. Add the eggs, vegetable oil, milk, sour cream, and vanilla extract, then mix until just combined.

4. Slowly stir in the hot coffee or hot water until the batter is smooth and thin.

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

6. Bake for 18 to 21 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.

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

8. Beat the softened butter until creamy, then add powdered sugar, cocoa powder, heavy cream, vanilla extract, and salt.

9. Whip the frosting until light and fluffy, adding a little more cream if needed for piping consistency.

10. Frost the cooled cupcakes and finish with chocolate sprinkles.