To Make the Cupcakes:
Preheat the Oven:
Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners.
Prepare the Batter:
In a large bowl, whisk together the flour, sugar, baking powder, and salt.
Add the butter, milk, eggs, and vanilla extract to the dry ingredients. Beat on medium speed until the batter is smooth and well combined.
Bake:
Divide the batter evenly among the muffin cups, filling each about ⅔ full.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cupcakes to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.
To Make the Pastry Cream Filling:
Heat the Milk and Cream:
In a medium saucepan, heat the milk and heavy cream over medium heat until it just begins to simmer.
Whisk the Egg Yolks:
In a medium bowl, whisk together the sugar, cornstarch, and egg yolks until smooth.
Temper the Eggs:
