Preheat the oven to 400°F (200°C). In a saucepan, combine water and butter over medium heat until the butter melts.

Add flour and salt, stirring vigorously until the mixture forms a ball and pulls away from the sides of the pan.

Remove from heat and let cool for 5 minutes. Gradually add eggs, mixing well after each addition until smooth.

Transfer the dough to a piping bag and pipe small mounds onto a baking sheet lined with parchment paper.

Bake for 20-25 minutes until puffed and golden. Remove from the oven and cool on a wire rack.

In a saucepan, combine milk, eggnog, and half the sugar. Heat over medium until just simmering.

In a separate bowl, whisk together the remaining sugar, cornstarch, and egg yolks until smooth.

Gradually whisk the hot milk mixture into the egg mixture, then return to the saucepan.

Cook over medium heat, stirring constantly until thickened. Remove from heat and stir in vanilla. Let cool.

In a mixing bowl, beat heavy cream, powdered sugar, and vanilla extract until soft peaks form.

Once the choux pastry has cooled, cut a small hole in the bottom of each puff.

Fill a piping bag with the eggnog pastry cream and pipe into each puff until filled.

Top with whipped cream and sprinkle with ground nutmeg before serving.