Preheat your oven to 325°F (163°C).

Finely crush gingersnap cookies in a food processor, then mix with sugar and melted butter. Press mixture into a 9-inch springform pan and chill for 15 minutes.

In a mixing bowl, beat cream cheese until smooth. Gradually add sugar and eggnog, mixing well.

Add eggs one at a time, mixing gently. Incorporate vanilla, nutmeg, cinnamon, and optional rum.

Wrap the bottom of the springform pan in aluminum foil and place it in a larger baking dish. Fill with hot water halfway up the sides.

Pour the filling over the crust and bake for 55-65 minutes until edges are set but center is slightly wobbly.

Turn off the oven and leave pie inside for 1 hour to cool gradually. Remove from oven and water bath.

Refrigerate uncovered until cool, then cover and chill for at least 4 hours or overnight.

Whip cream for topping, slice the pie with a warm knife, and garnish with nutmeg or cinnamon and decorative cookies.