Preheat your oven to 350°F (175°C). Line a muffin tin with cupcake liners.

In a large bowl, mix the flour, sugar, baking powder, and salt.

Add the softened butter, eggs, vanilla extract, and milk to the dry ingredients. Use an electric mixer to blend everything together until smooth and creamy.

Spoon the batter evenly into the cupcake liners, filling each about two-thirds full.

Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean. Let the cupcakes cool in the tin for 5 minutes before transferring to a wire rack to cool completely.

In a medium saucepan, heat the milk over medium heat until it’s just about to simmer. Remove from heat.

In a separate bowl, whisk together the egg yolks, sugar, and cornstarch until smooth and pale.

Slowly pour the hot milk into the egg mixture while whisking constantly to temper the eggs.

Return the mixture to the saucepan and cook over medium heat, stirring constantly, until it thickens to the consistency of pudding.

Remove from heat and stir in the vanilla extract and butter until smooth. Transfer the custard to a bowl, cover with plastic wrap, and refrigerate until it’s cool and firm (about 1 hour).

In a heatproof bowl, add the chopped dark chocolate.

Heat the heavy cream in a small saucepan until it’s just about to simmer, then pour it over the chocolate.

Let the mixture sit for 2-3 minutes, then stir until the chocolate is fully melted and the ganache is smooth. Let it cool slightly before using.

Once the cupcakes have cooled, use a small knife or cupcake corer to create a hole in the center of each cupcake.

Fill each hole with the chilled custard filling, making sure to pack it in without overflowing.

Spoon the chocolate ganache over the top of each filled cupcake, covering the custard with a luscious layer of rich chocolate.

Allow the ganache to set for about 15 minutes before serving.