Preheat oven to 425°F (220°C) and line two baking sheets with parchment paper.

In a saucepan, combine water, butter, salt, and sugar; bring to a full boil.

Add flour all at once, stirring until a smooth ball forms and pulls away from the sides (30–45 seconds). Return to low heat for 1–2 minutes to slightly dry the dough.

Transfer to a mixing bowl and cool for 3–4 minutes. Beat in eggs one at a time until the dough is smooth, glossy, and forms a soft 'V' shape when lifted.

Pro Tip: Don’t rush drying or cooling—proper moisture control helps the puffs rise perfectly.

Pipe 1½-inch rounds of dough onto lined sheets, spacing 2 inches apart. Smooth peaks with a damp fingertip.

Spritz the oven with water or place a small pan of water inside for steam.

Bake at 425°F (220°C) for 10 minutes, then reduce to 350°F (175°C) and bake for 15–18 minutes more until golden and crisp.

Turn off oven, crack the door, and cool puffs inside for 10 minutes before transferring to a rack.

Baking Secret: Never open the oven during the first 20 minutes—undisturbed steam is crucial for tall, airy puffs.

Make pastry cream by heating milk with sugar and salt.

Whisk egg yolks, sugar, and cornstarch separately, then temper with hot milk. Return to the pan and cook until thickened. Remove from heat, stir in butter and vanilla, strain smooth, and chill for 1 hour.

Slice cooled puffs horizontally, fill with chilled pastry cream, and replace the tops.

Dust with powdered sugar or drizzle with chocolate ganache before serving.

Assembly Note: Fill puffs within 2–3 hours of serving to keep the shells crisp and the interiors creamy.