Preheat oven to 400°F. In a small saucepan, bring water and butter to a rolling boil over medium heat. Add flour and salt all at once; beat until blended. Cook, stirring vigorously, until a film forms at the bottom of the pan, about 4 minutes. Remove from heat; let stand for 10 minutes.

Add eggs, 1 at a time, beating well after each addition until smooth. Continue beating until mixture is smooth and shiny. Drop dough by 1-inch balls 1-1/2 inches apart onto parchment-lined baking sheets.

Bake until puffed, very firm, and golden brown, 25-30 minutes. Cool on wire racks.

Whisk together pudding mix and milk for 2 minutes or until thickened; let stand for 5 minutes. Fold in whipped topping.

Cut puffs in half. Fill cream puffs with vanilla filling; replace tops. Dust with confectioners' sugar; serve immediately.