Boston Cream Pie Cupcakes

INGREDIENTS

For the pastry cream:

large egg yolks

1/2 cup

sugar

1/4 cup

cornstarch

salt

2 cups

milk

1 1/4 tsp

vanilla extract

For the cupcakes:

9 tbsp

unsalted butter, at room temperature, plus more for greasing pans

2 1/4 cups

all-purpose flour, plus more for pans

2 1/4 tsp

baking powder

3/4 tsp

salt

3/4 cup

milk

large eggs plus 1 egg yolk

1 1/2 cups

sugar

1 1/2 tsp

vanilla extract

For the ganache:

9 oz

semisweet or bittersweet chocolate, finely chopped

1 cup

heavy cream

1 1/2 tbsp

light corn syrup