Preheat & Prep
Preheat oven to 350°F (175°C) and line a muffin tin with 12 paper liners.

Make the Cupcake Batter
In a medium bowl, whisk together flour, baking powder, and salt.
In a separate large bowl, beat butter and sugar until light and fluffy. Add eggs one at a time, mixing well after each. Stir in vanilla extract.
Alternate adding the dry mixture and milk into the wet mixture, starting and ending with the dry ingredients. Mix until just combined.

Bake the Cupcakes
Fill liners about ⅔ full and bake for 16–18 minutes or until a toothpick comes out clean.
Cool completely on a wire rack.

Make the Pastry Cream
Heat milk in a saucepan over medium heat until warm.
In a bowl, whisk together egg yolks, sugar, and cornstarch. Gradually pour the warm milk into the egg mixture, whisking constantly.
Return the mixture to the saucepan and cook over medium heat, whisking constantly, until thickened.
Remove from heat, stir in vanilla and butter, and let cool. Chill in the fridge before using.

Fill the Cupcakes
Use a cupcake corer or paring knife to cut a small hole in the center of each cupcake.
Fill each hole with the chilled pastry cream using a piping bag or spoon.

Prepare the Ganache
Heat heavy cream in a small saucepan until just beginning to bubble.
Pour over chocolate chips in a bowl and let sit for 1 minute. Stir until smooth and glossy.

Top the Cupcakes
Spoon ganache over the filled cupcakes or dip the tops into the ganache.
Let set at room temperature or chill slightly before serving.