You can use sweet or savory fillings in this puff pastry shell.

4 tablespoons unsalted butter, cut into small pieces

Pinch of salt

1/2 cup plus 1 tablespoon water

1/2 cup all-purpose flour

3 large eggs

1 large egg white

Preheat the oven to 375 degrees. Line a baking sheet with parchment paper, and set aside. Combine butter, salt, and 1/2 cup water in a small saucepan, and place over medium heat. Cook until butter is melted and the water just comes to a boil.
Remove from heat, add flour, and stir rapidly. Return the pan to the heat, and cook mixture, stirring constantly, until it comes together and pulls away from the sides of the saucepan, about 5 minutes. Remove saucepan from heat, and let cool for 5 minutes.
Add eggs one at a time, beating until they are completely incorporated and the pastry is smooth. Transfer the pastry to a bag fitted with a small coupler. Pipe about 1/2 tablespoon of the pastry into a mound on the prepared baking sheet; continue piping until all the pastry is used, spacing pastry about 1 1/2 inches apart. Combine egg white with remaining 1 tablespoon of water, and brush the top of each mound with the egg wash. Bake until the puffs are golden brown all over, about 30 minutes. Remove from the oven, transfer to a wire rack, and let cool completely.