Cream Puffs Ingredients Custard Filling: 1 large egg 4 large egg yolks 3 cups milk 2/3 cup sugar 2/3 cup flour 1/4 teaspoon salt 3 tablespoons unsalted butter 1 tablespoon pure vanilla extract 1 cup heavy cream Choux Batter 1 cup water 1/2 cup (1 stick) unsalted butter 2 teaspoons sugar 1/4 teaspoon salt