1. Preheat the oven to 400°F and line a large baking sheet with parchment paper.

2. In a medium saucepan, combine the water, butter, granulated sugar, and salt. Bring to a full boil over medium heat.

3. Add the flour all at once and stir quickly until the dough pulls away from the sides of the pan and forms a smooth ball.

4. Continue cooking the dough for 1 minute, then transfer it to a mixing bowl and let it cool for 5 minutes.

5. Add the eggs one at a time, mixing well after each addition, until the dough is glossy, thick, and smooth.

6. Spoon or pipe 2-tablespoon mounds of dough onto the prepared baking sheet, leaving space between each puff.

7. Bake for 15 minutes at 400°F, then reduce the oven temperature to 350°F and bake for 20 to 25 minutes more, until deeply golden and firm.

8. Turn off the oven, crack the door, and let the shells rest for 10 minutes before transferring them to a wire rack to cool completely.

9. Beat the heavy cream, powdered sugar, vanilla extract, and instant vanilla pudding mix until thick, fluffy, and pipeable.

10. Slice each cooled shell in half, fill with cream, replace the tops, and dust with powdered sugar before serving.