Make the Vanilla Cupcakes:

• Preheat oven to 350°F (175°C) and line a 12-cup muffin tin with cupcake liners.
• In a large bowl, whisk together flour, sugar, baking powder, and salt.
• Add butter, eggs, milk, and vanilla extract, then beat until smooth.
• Fill each cupcake liner ⅔ full with batter.
• Bake for 18-20 minutes, or until a toothpick inserted in the center comes out clean.
• Let cupcakes cool completely before filling.

2. Prepare the Custard Filling:

• In a saucepan, whisk together milk, egg yolks, sugar, and cornstarch.
• Cook over medium heat, stirring constantly, until thickened (5-7 minutes).
• Remove from heat and stir in vanilla extract.
• Transfer to a bowl, cover with plastic wrap pressed against the surface, and refrigerate until cool.

3. Make the Chocolate Ganache:

• Heat heavy cream in a small saucepan until it simmers (do not boil).
• Pour over chopped chocolate and let sit for 5 minutes.
• Stir until smooth and glossy. Let cool slightly to a pourable consistency.

4. Assemble the Cupcakes:

• Use a small knife or cupcake corer to cut a hole in the center of each cupcake.
• Spoon or pipe custard filling into each cupcake.
• Spoon ganache over the top, letting it drip slightly down the sides.

5. Serve & Enjoy:

• Let the ganache set for 10 minutes before serving.
• Enjoy fresh or store for later!