Preheat oven to 375°F (191°C). Line 14 cups from 2 12-count muffin pans with liners.

Over high heat, boil the water in a small saucepan. Pour the unsweetened cocoa powder into a medium sized bowl and mix with boiling water until smooth. Allow to cool to room temperature by placing in the refrigerator as you prepare the other ingredients.

Whisk together the flour, baking powder, and salt in a medium sized bowl. Set aside.

In a large bowl, using an electric hand or stand mixer, cream the softened butter and sugar until light and fluffy. Add the eggs, one at a time, beating until smooth. Scrape down the sides of the bowl as needed. Beat in the vanilla extract. Slowly add the flour mixture and beat only until *just* combined. In a steady stream, add the cooled cocoa mixture and stir until smooth.

Fill each muffin tin 3/4 of the way full with batter. Bake for 16-19 minutes, keeping an eye on them to avoid even the slightest burning (which will lend dry cupcakes). My cupcakes took 17 minutes and a toothpick inserted in the middle came out clean. Remove from oven and place on a wire rack to cool before frosting.

In a large bowl using a handheld or stand mixer fitted with a paddle attachment, beat the butter on medium speed until smooth, about 2 minutes. Stop the mixer and add confectioners’ sugar, Nutella, heavy cream, and vanilla extract. Beat on low speed for 30 seconds, then increase to medium-high speed and beat for 2 full minutes. Add up to 1/2 cup more confectioners’ sugar if frosting is too thin or another Tablespoon of cream if frosting is too thick. Add a pinch of salt if frosting is too sweet. (I always add 1/8 teaspoon salt.)

Frost cooled cupcakes with a piping tip, knife, or icing spatula. I used Wilton #12 round tip. Decorate with candies, if desired.

Serve immediately. Store leftover cupcakes in the refrigerator for up to 5 days.