Preheat oven to 350°F (180°C). Line a standard cupcake pan with 12 baking cups and a second pan with 6 cups.

Sift together the flour, baking soda and salt on a sheet of wax paper.

Beat the butter on medium speed until fluffy. Add the sugar. Beat on medium speed until well mixed.

Add the eggs one at a time, mixing slowly after each addition.

Combine the vanilla extract and milk in a large liquid measuring cup.

Reduce the speed to low. Add one third of the flour mixture to the butter mixture; then gradually add a third of the milk mixture, beating until well incorporated. Add another third of the flour mixture, followed by a third of the milk mixture. Stop to scrape down the bowl as needed. Add the remaining flour mixture, followed by the remaining milk mixture, and beat until just combined.

Add the cocoa powder, beating on low until just incorporated.

Using a standard size ice cream scoop, fill each cupcake paper with batter, so that the wells are two-thirds full. Bake for 18–20 minutes (start checking at 15 minutes) or until a toothpick inserted into the center of a cupcake comes out clean. Transfer the pans to a wire rack to cool completely.

Lay a large piece of wax paper on the work surface.

Combine the heavy cream and chocolate in a medium heatproof bowl. Fill a medium saucepan with an inch or two of water and place over medium-low heat. Place the bowl over the saucepan and let the mixture melt, stirring until it is shiny and smooth.

Remove the bowl of chocolate ganache from the saucepan; let cool slightly, for 2–3 minutes.

Carefully dip each cupcake top in the warm ganache, twisting your wrist as needed to make sure the cupcake top gets completely coated. To prevent drips, quickly turn the cupcake right side up and place on the wax paper. Allow the ganache to set for 5 minutes before serving.