Preheat oven to 400°F (200°C). In a saucepan, combine water, butter, and salt. Bring to a boil.

Remove from heat and add flour all at once, stirring vigorously until a smooth dough forms and pulls away from the sides of the pan.

Transfer dough to a bowl and let cool slightly. Add eggs one at a time, mixing until fully incorporated.

Spoon or pipe dough onto a baking sheet lined with parchment paper. Bake for 30 minutes, or until golden brown and puffed up. Let cool completely.

In a bowl, whip heavy cream, powdered sugar, and vanilla extract until stiff peaks form.

Cut cream puffs in half and fill with the whipped cream.

Serve immediately.