1. In a medium saucepan, combine water and butter over medium heat until butter melts. Bring to a gentle boil.

2. Reduce heat and add flour all at once. Stir quickly until the dough forms a smooth ball. Let cool for 5 minutes.

3. Add eggs one at a time, beating after each addition until the dough is glossy and pipeable.

4. Transfer dough to a piping bag with a round tip. Preheat oven to 400°F (200°C). Pipe 1.5-inch rounds on a parchment-lined baking sheet.

5. Bake for 20–25 minutes until puffed and golden. Cool completely on a wire rack.

6. For the filling, whisk together milk, sugar, cornstarch, and nutmeg in a saucepan. Cook over medium heat, stirring constantly until thickened.

7. Remove from heat and stir in vanilla extract. Cool the custard completely.

8. Fold in whipped cream until smooth and airy.

9. Slice cream puffs in half. Fill the bottom halves with eggnog cream and replace the tops. Dust with powdered sugar or extra nutmeg.