Preheat oven to 400°F (200°C) and prepare baking sheets by greasing or lining with parchment paper.
Bring water, cubed butter, and salt to a rolling boil in a large saucepan.
Add flour all at once, then add nutmeg, and stir vigorously until the mixture pulls away from the sides.
Remove from heat and let the dough rest for 5 minutes.
Beat in eggs one at a time, mixing well after each addition until the dough is smooth and glossy.
Drop rounded tablespoonfuls of dough onto the baking sheets spaced 1 inch apart.
Bake for 30 to 35 minutes until the puffs are firm, deeply golden, and fully set.
Pierce each puff immediately with a knife tip to release steam and cool completely on a wire rack.
Beat heavy cream until it begins to thicken, then add confectioners’ sugar, eggnog, vanilla extract, and nutmeg.
Continue beating until soft peaks form for the whipped cream filling.
Cut the top third off each cooled cream puff and spoon or pipe in the eggnog whipped cream.
Replace the tops, dust with confectioners’ sugar, and serve immediately.