Prepare two piping bags by fitting one with a coupler and medium round tip and the other with a coupler and large star tip. Line a cookie sheet with a silicone baking mat. Set everything aside.

To a 2-quart saucepan set over high heat, add the water and butter. Bring to a boil and cook until butter melts.

Remove the saucepan from the heat. Add flour to the pan and stir vigorously with a wooden spoon or rubber spatula until a large ball of dough forms.

Add one egg to the dough and stir until fully incorporated. One at a time, continue adding and incorporating the eggs. The choux dough will be loose at first, then thicken and stiffen as more egg is incorporated.

Using a large spoon, transfer the dough into the prepared piping bag. Close the bag, then pipe mounds of batter, 1 to 2 inches wide and 2 inches apart, onto the prepared baking sheet.

Bake at 400°F. for 35 minutes. Important: Do not open the oven door until the shells are golden brown. There are no leaveners in the dough - it needs heat to help it rise and “puff up”.

Remove pastry shells from the oven and transfer them to a wire cooling rack. Let them cool completely before adding whipped cream. Meanwhile, make the cream puff filling.

Pour heavy whipping cream into a large metal mixing bowl. Using a handheld mixer fitted with whisk attachments, beat the whipping cream at high speed until soft peaks form.

Add the powdered sugar, cornstarch, and vanilla extract. Continue mixing on high speed until stiff peaks form.

Refrigerate the filling for at least 30 minutes before transferring it to a piping bag fitted with a star tip.

Pipe whipped cream onto puffs and refrigerate or freeze until ready to serve.