In a saucepan, bring the water, butter, sugar, and salt to a full boil.
Remove from heat and add the flour all at once. Stir vigorously with a wooden spoon.
Return to medium heat and cook, stirring constantly, until the dough forms a ball and pulls away from the sides. A thin film will form on the bottom, this is normal.
Remove from heat and let cool for 2 minutes.
Add the eggs one at a time, mixing fully after each addition. You may not need all four eggs. The dough should be glossy and smooth, forming a slow “V” shape when lifted with a spatula.
Shaping (no piping bag needed)
Using two spoons, form small mounds about 1½ inches (3–3.5 cm) wide on a lined baking sheet. Lightly smooth the tops with a damp fingertip. Keep them small, this ensures even baking and a light interior.
Baking
340°F (170°C) for 15 minutes. Increase to 355°F (180°C) for 10–15 minutes. Do not open the oven early. They should be deeply golden, light, and firm.
Turn off the oven, crack the door slightly, and let them sit inside for 10 minutes to dry. Cool completely on a rack.
Chocolate Pastry Cream
Heat the milk until steaming.
Whisk yolks and sugar until pale. Add cornstarch.
Slowly pour in the hot milk while whisking. Return to heat and cook until thick and bubbling.
Remove from heat. Add chocolate, butter, and salt. Stir until smooth. Press plastic wrap directly onto the surface and chill completely. The cream should be firm once cold, this is essential for the diplomat texture.
Chocolate Diplomat Cream
Whip the heavy cream to soft peaks.
Whisk the pastry cream until smooth.
Fold in one-third of the whipped cream to loosen. Gently fold in the remaining cream until airy but stable. The final texture should be silky and light, yet structured enough to hold its shape.
Assembly
Slice a small lid off each puff. Fill generously.
Replace the tops and dust lightly with powdered sugar.
Serve within 4–6 hours for best texture.
Notes
Use 55% dark chocolate for a rounder, more Parisian flavor.
Smaller puffs bake more evenly and stay crisp.
Fill shortly before serving to preserve the shell texture.