Whisk together the cornstarch and half the sugar. Add egg and egg yolks and mix into a smooth paste, set aside.

Bring the milk, remaining sugar, butter, salt, and vanilla bean to a gentle boil in a medium-large saucepan.

Slowly, and in small amounts, whisk the hot milk mixture into the egg mixture. Once the egg mixture is warm to the touch, pour it back into the pot.

Return the custard to the stovetop and bring to a boil over medium heat, whisking continuously for 3 minutes, until thick and glossy. In order to properly cook the cornstarch in the custard you need to cook the pastry cream for the full 3 minutes.

Transfer to a shallow container and cover with plastic-wrap, placed directly on the surface of the pastry cream.

Chill in the refrigerator for at least 30 minutes. The pastry cream can be stored for up to 5 days.

Makes 2 cups pastry cream. This recipe is easily doubled or halved.