1. Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.

2. In a saucepan, bring butter, water, and salt to a boil. Reduce heat and add flour all at once, stirring vigorously until mixture forms a ball and pulls away from the sides.

3. Remove from heat and let cool for 5 minutes.

4. Beat in eggs one at a time, mixing until smooth and glossy.

5. Transfer dough to a piping bag fitted with a large round tip. Pipe 1½-inch mounds onto the baking sheet, spacing 2 inches apart.

6. Bake for 25–30 minutes, or until puffed and golden brown. Cool completely on a wire rack.

7. To make the eggnog filling, whisk together eggnog, sugar, cornstarch, egg yolks, vanilla, and nutmeg in a saucepan.

8. Cook over medium heat, whisking constantly, until thickened (about 6–8 minutes). Remove from heat, cover with plastic wrap directly on the surface, and chill completely.

9. Fold whipped cream into cooled eggnog custard to make a light cream.

10. Cut tops off puffs, fill with eggnog cream, and replace tops. Dust with powdered sugar before serving.