Preheat the oven to 400°F. Line two sheet pans with parchment paper and set aside.
In a heavy saucepan, heat butter, water, salt, and sugar over medium heat.
When butter has melted completely and mixture begins to boil, remove from heat.
Immediately dump the flour into the saucepan and stir with a wooden spoon until it is completely incorporated.
Return the mixture to medium heat and cook while stirring, until the dough pulls away from the sides of the pan and forms a smooth ball (about 2 minutes).
Remove the dough from the heat and allow to cool for about 5 minutes.
Beat each egg, one at a time, into the flour mixture with a wooden spoon (you can also use a standing or hand mixer). The dough will separate when each egg is added, but will come back together after mixing.
After all eggs have been incorporated, and the mixture is smooth and glossy, transfer to a large piping bag fit with an open round tip.
Pipe 1 1⁄2” rounds of the dough onto the prepared sheet pans, spacing each ball two inches apart.
Dip your finger into cold water and smooth down any peaks left behind from piping.
Bake the puffs for 10 minutes at 400°F, then 20-25 minutes more at 350°F. Prop open oven door for 15 minutes after baking while keeping the cream puffs inside.
Transfer cream puffs to a wire cooling rack and cool completely.
Use a wire whisk attachment on your standing mixer or hand mixer to beat heavy cream until soft peaks form.
Add the powdered sugar (more or less to taste) and continue beating until stiff peaks form. Do not overbeat or cream will turn to butter.
Slice the tops off of the cream puffs (a serrated knife works best).
Mound the whipped cream into the cream puff or use a pastry bag fit with an open star tip (Tip #1M) to pipe swirled whipped cream into the centers.
Place the tops of the cream puffs onto the whipped cream filling and sprinkle with powdered sugar.
The unfilled cream puffs can be stored in the refrigerator up to 3 days or frozen for up to 1 month. However, the flavor and texture is best when made and served the same day.
The choux pastry puffs up, leaving a hollow center due to the moisture in the dough. Leaving the oven cracked open after baking allows the outer shell to dry out and crisp without the cream puff collapsing.