In a medium saucepan, bring water and unsalted butter to a rolling boil over medium heat. Remove from heat and quickly stir in flour until the mixture pulls away and forms a ball, about 2-3 minutes.

Allow the dough to cool for 5 minutes. Add eggs one at a time, mixing vigorously until fully incorporated and smooth, about 5 minutes.

Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper. Transfer dough into a piping bag and pipe small mounds on the sheet.

Bake for 25-30 minutes until puffed and golden brown. Avoid opening the oven door early.

Remove from oven and cool on a wire rack for at least 30 minutes.

While puffs cool, whip heavy cream with powdered sugar and vanilla until stiff peaks form, about 3-4 minutes.

Slice cooled cream puffs in half horizontally and fill with whipped cream. Replace the top half to create sandwiches.