Apple Empanadas with Almond Pastry Cream

Name: Apple Empanadas with Almond Pastry Cream
Ingredients: 1 large egg, beaten; 2 to 3 tablespoons unsalted butter; 3 large Granny Smith apples, cored, peeled and cut into 1-inch dice; Turbinado sugar; 3 tablespoons brown sugar; 1 teaspoon ground cinnamon; Pinch salt; Bench flour, for dusting; Almond Pastry Cream, at room temperature, recipe follows; 1 box frozen puff pastry, thawed according to package directions; 1 1/2 cups whole milk; 1/2 cup sugar; 2 tablespoons almond paste; 4 large egg yolks; 2 tablespoons cornstarch; 3 tablespoons unsalted butter