1. Drop 2-tbsp mounds onto sheets (or pipe for neat rounds).
2. Bake at 425°F for 15 minutes, then reduce to 350°F (175°C) and bake 20–25 minutes until golden and firm.
3. Turn off oven, crack door, and let puffs dry 10 minutes.
4. Poke each puff with a toothpick to release steam; cool completely.

3. Make the Vanilla Custard

1. Heat milk until steaming (not boiling).
2. In a bowl, whisk yolks, sugar, cornstarch, and salt until pale.
3. Slowly whisk hot milk into yolk mixture.
4. Return to saucepan, cook over medium heat until thick and bubbling (~2–3 mins).
5. Remove from heat, stir in vanilla. Cover with plastic wrap directly on surface and chill at least 1 hour.

4. Fill & Serve

1. Slice puffs in half. Spoon or pipe custard into bottoms.
2. Replace tops. Dust with powdered sugar or drizzle with chocolate sauce.