In a medium saucepan, combine 1 cup of water, ½ cup of unsalted butter, and 1 tablespoon of sugar. Bring this mixture to a rolling boil over medium heat, then remove it from the heat. Add 1 cup of all-purpose flour all at once and stir vigorously until a dough forms and pulls away from the sides of the pan, about 2 minutes. Allow the dough to cool for 10 minutes before moving to the next step.

Once your dough has cooled slightly, add 4 large eggs, one at a time, mixing thoroughly after each addition. The mixture should be smooth and glossy when you finish.

Preheat your oven to 400°F (200°C) and line two baking sheets with parchment paper. Using a piping bag fitted with a large round tip, pipe about 2-inch round mounds of the choux pastry dough onto the prepared sheets, leaving space between them for expansion. Bake for 20-25 minutes or until they are puffed and golden brown.

While the cream puffs cool, whip 1 cup of heavy cream with 2 tablespoons of sugar and 1 teaspoon of pure vanilla extract in a mixing bowl until soft peaks form, about 3-5 minutes.

Once the baked puffs have cooled completely, use a serrated knife to gently slice each puff in half horizontally. Spoon or pipe the whipped cream filling generously into the bottom half of each puff and place the tops back on.

Dust the filled cream puffs with powdered sugar or drizzle with chocolate sauce before serving.