Instructions

1. 1

   Preheat the oven to 350°F and line a 12-cup muffin pan with cupcake liners. In a medium bowl, whisk together the flour, baking powder, and salt until evenly combined.

2. 2

   In a separate large bowl, beat the butter and sugar until the mixture looks pale and fluffy, about 2 to 3 minutes. Add the eggs one at a time, mixing until smooth after each addition. Stir in the vanilla extract.

3. 3

   Add the dry ingredients in two additions, alternating with the milk. Mix just until the batter is smooth and thick with no dry streaks left behind.

4. 4

   Divide the batter evenly between the cupcake liners, filling each about two-thirds full. Bake for 18 to 22 minutes, until the tops spring back lightly when touched and the edges are just turning golden. Let the cupcakes cool completely before filling.

5. 5

   While the cupcakes cool, make the custard filling. Heat the milk in a saucepan over medium heat until steaming but not boiling. In another bowl, whisk together the sugar, cornstarch, and egg yolk until smooth.

6. 6

   Slowly pour a little of the warm milk into the egg mixture while whisking constantly. Return everything to the saucepan and cook over medium heat, stirring continuously, until the custard thickens to a pudding-like texture that coats the back of a spoon. Remove from the heat and stir in the butter and vanilla.

7. 7

   Transfer the custard to a bowl and press plastic wrap directly against the surface to prevent a skin from forming. Chill for at least 30 minutes, until cool and thick.

8. 8

   Use a small knife or cupcake corer to cut a hole in the center of each cupcake. Spoon or pipe the custard into the center until just full.

9. 9

   Heat the heavy cream until steaming, then pour it over the chocolate chips. Let it sit for 2 minutes before stirring until smooth and glossy. Spoon the ganache over the tops of the filled cupcakes, letting it drip slightly down the sides.

10. 10

    Chill the cupcakes for about 15 minutes so the ganache sets with a soft shine.