Preheat the Oven - Set the oven racks to upper-middle and lower-middle positions. Preheat to 425°F (218ºC). Line two sheet pans with parchment paper and set them aside.

Make the Dough - In a large heavy-bottomed saucepan, add 1 cup of water, sugar, salt, and butter. Bring to a boil over medium-high heat and stir until the butter fully melts, about 2 minutes.

Cool the Dough - Transfer the dough to a bowl of a stand mixer fitted with a paddle. Slowly stir on low speed (setting 2) to cool to 130°F (54ºC) or just below, about 2 to 3 minutes.

Add the Eggs in Stages - Add eggs one at a time, mixing on medium-low speed (setting 4) until each egg is fully incorporated, about 30 to 45 seconds per egg.

Piping the Dough - Add a large plain tip to a piping bag. Option to lightly grease the inside of the pastry bag with cooking spray. Add the dough to the pastry bag.

Brush on Egg Wash - In a small bowl, whisk together one egg and 1 tablespoon of water. Brush the tops and sides of each dough ball with the egg wash.

Gradual Baking Process - Place the sheet trays in the oven. Bake for a sequence of temperatures without opening the oven door.

Make the Whipped Cream - In a stand mixer fitted with the whisk attachment, add heavy cream, powdered sugar, and 1 teaspoon vanilla extract. Whip on medium-low speed to stiff peaks.

Piping the Cream - Working in batches, add the whipped cream to a pastry bag fitted with a large star tip. Pipe the whipped cream into the pastry bottoms.

Top with Sugar - Sprinkle powdered sugar on top of each cream puff. Serve immediately, or refrigerate, uncovered.