When my mom would make her custard, I couldn't wait to just take some spoonfulls when it was still warm. She would always use lemon peel in her custard, when she would take the lemon peel, she would always put it in a bowl because she knew I wanted to lick the peels. I am guilty of still doing that. If you do use lemon peel, break it up into 1-3 pieces so the custard is easier to stir. This recipe is great for any pastry, cakes, pies, tarts or by itself.
In a heavy saucepan, stir together the milk and 1/4 cup of sugar. Bring to a boil over medium heat.
In a medium bowl, whisk together the egg yolks and egg. Stir together the remaining sugar and cornstarch; then stir them into the egg until smooth. When the milk comes to a boil, drizzle it into the bowl in a thin stream while mixing so that you do not cook the eggs. Return the mixture to the saucepan, and slowly bring to a boil, stirring constantly so the eggs don't curdle or scorch on the bottom. Add Lemon Peel if desired.
When the mixture comes to a boil and thickens, remove from the heat and remove lemon peel. Stir in the butter and vanilla, mixing until the butter is completely blended in. Pour into a heat-proof container and place a piece of plastic wrap directly on the surface to prevent a skin from forming. Refrigerate until chilled before using.