Preheat the oven to 350F. Line a cookie sheet with parchment paper and set aside
In the bowl of a stand mixer fitted with a paddle attachment OR with a large bowl and a hand-mixer combine the butter and the sugar. Cream together for at least 3 minutes in the stand mixer or 5 minutes with the hand mixer. Scrape the sides of the bowl with a non-stick spatula and add in the egg yolks and both extracts. Mix again. Add in the eggnog and mix again, mixture may look curdled if the eggnog is not room temperature. That is ok!
Add in flour, baking powder and salt. Mix just to combine. Dough will be very soft and sticky. Using a cookie scoop (or your hands) scoop out 2 tablespoon sized balls of dough. Place the dough on the lined cookie sheet and bake for 6-8 minutes, until tops look set and cookies no longer look "wet" on top. Remove from oven and let cool.