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

In a saucepan, combine water, butter, sugar, and salt. Bring to a boil, then stir in flour and return to low heat until mixture forms a ball.

Cool for 5 minutes, then add eggs one at a time, mixing until glossy and elastic.

Pipe small rounds onto the baking sheets, smoothing any peaks.

Bake at 425°F (220°C) for 10-12 minutes, then reduce to 350°F (175°C) and bake for another 18-20 minutes until golden brown.

Prepare the pastry cream by heating eggnog and milk, then whisking egg yolks, sugar, and cornstarch. Combine and heat until thickened.

Stir in butter, vanilla, nutmeg, and salt. Cool before chilling in the refrigerator.

Whip heavy cream with powdered sugar until stiff peaks form.

Fill cooled puffs with eggnog pastry cream and dust with powdered sugar or cocoa before serving.