In a large bowl, combine the flour, salt, baking soda, baking powder, ground cinnamon, and nutmeg.
Cream together the butter, brown sugar, and granulate sugar, until light and fluffy, about two minutes.
Beat in the vanilla extract, then the egg, then the eggnog, until just combined.
Slowly beat in the flour mixture, about a half of a cup at a time, until just combined.
Stir in the white chocolate chips.
Refrigerate for 24 hours. (Note: If you decide to refrigerate for a shorter amount of time (like an hour), the cookies will totally work, but they won't be puffy. Still delicious, but flatter and chewier.)
Preheat your oven to 350 degrees.
The dough will be very sticky. Spray a cookie scoop with cooking spray. Scoop cookie dough onto a parchment paper or silicon mat lined baking sheet . Spray your hands with cooking spray and roll the cookie balls to make them smooth. The cookies should be about two inches apart to allow for some spreading.
Bake for 14 minutes, rotating the pan halfway through baking. Remove from the oven, allow to sit on the pan for about two minutes, then remove to a cooling wrack to cool completely before storing in an airtight container.
Room temperature butter means that you can push your finger into the butter a little bit with it making a dent, but it doesn't go all the way through.