Preheat oven to 425°F (220°C).
In a saucepan, bring water, butter, and salt to a boil.
Add flour all at once and stir vigorously until mixture forms a ball.
Remove from heat and let cool for 5 minutes.
Add eggs one at a time, beating well after each addition.
Drop by tablespoonfuls onto a baking sheet.
Bake for 20-25 minutes or until golden brown.
Let cool completely.
For the cream filling, whip the heavy cream, sugar, and vanilla extract until stiff peaks form.
Cut the tops off the puffs and fill with the whipped cream.
Replace tops and serve.