Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.

In a medium saucepan, combine water, butter, and salt. Bring to a rolling boil over medium heat.

Remove from heat and immediately add all the flour. Stir vigorously with a wooden spoon until the dough forms a ball and pulls away from the sides of the pan.

Return the saucepan to low heat and cook, stirring constantly, for 1-2 minutes to dry out the dough slightly.

Transfer the dough to a large bowl of a stand mixer fitted with the paddle attachment. Let it cool for 5 minutes.

Add the eggs one at a time, beating well after each addition, until the dough is smooth and glossy. The dough should be thick but still pipeable.

Spoon or pipe mounds of dough (about 2 tablespoons each) onto the prepared baking sheet, leaving about 2 inches between them.

Bake for 20 minutes at 400°F (200°C), then reduce oven temperature to 350°F (175°C) and bake for another 10-15 minutes, or until golden brown and puffed.

Once baked, pierce each cream puff with a sharp knife or skewer to allow steam to escape and prevent them from becoming soggy. Let them cool completely on a wire rack.

In a chilled bowl, beat the cold heavy cream with an electric mixer until soft peaks form.

Gradually add the powdered sugar and vanilla extract, and continue beating until stiff peaks form.

Once the cream puffs are completely cool, slice them in half horizontally or make a slit in the side.

Fill the bottom half of each cream puff generously with the whipped cream filling.

Place the top half of the cream puff back on top.

Dust the tops of the cream puffs with powdered sugar just before serving.