Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.

In a medium saucepan, combine 1 cup of water and 1/2 cup of unsalted butter. Heat over medium until the butter melts and the mixture reaches a rolling boil. Stir in 1 cup of all-purpose flour until a cohesive dough forms.

Remove from heat and let the dough cool for 5 minutes. Gradually add the 4 room temperature eggs, mixing well after each addition.

Use a piping bag to dollop equal-sized mounds of dough onto the prepared baking sheet, spacing them 2 inches apart.

Bake for 20-25 minutes until the puffs are golden and have doubled in size. Avoid opening the oven door during baking.

While the puffs cool, whip 1 cup of heavy cream, 1/4 cup of sugar, 2 tablespoons of lemon zest and 1/4 cup of lemon juice until soft peaks form.

Once cooled, fill each puff with the lemon cream mixture using a piping bag or by slicing the tops off and spooning the filling inside.