Heat the oven to 425°F (220°C) and line a baking sheet with parchment paper.

Place the water, butter, and salt in a saucepan and bring the mixture to a full boil over medium heat.

Remove the saucepan from the heat, add all the flour at once, and stir vigorously until a smooth dough forms.

Return the pan to medium-low heat and cook for 1 to 2 minutes, stirring constantly, until the dough pulls away from the sides and leaves a thin film on the bottom.

Transfer the dough to a bowl and cool for 5 to 10 minutes. Add the lightly beaten eggs gradually, beating well after each addition, and stop when the dough is smooth, glossy, and thick enough to hold a soft peak.

Pipe or spoon 12 mounds onto the prepared baking sheet, leaving space between them. Smooth any pointed tops with a damp fingertip.

Bake at 425°F for 15 minutes, then reduce the oven to 375°F (190°C) and bake for another 15 to 20 minutes, until the puffs are deeply golden and firm.

Turn off the oven, pierce each puff once with a skewer or knife to release steam, and leave them in the switched-off oven for 5 to 10 minutes. Transfer the puffs to a rack and cool completely.

Whip the cold cream, powdered sugar, and vanilla to medium-stiff peaks. Fold in the finely diced strawberries, then slice the cooled puffs horizontally or cut a small opening in the side and fill them with the strawberry cream.