Preheat oven to 325 degrees.
Butter/grease a 9" springform pan.
In a food processor, pulse Oreos until finely ground, then add melted butter and pulse until well combined(about 30 seconds).
Place Oreo crumbs in the prepared springform pan, and use your hands, knuckles, the bottom of a cup, or a silicone spatula to firmly press crumbs down, forming a crust.
In a mixing bowl, add cream cheese and sugar. Use an electric hand mixer, on low speed, to whip the cream cheese and sugar. Don't over beat, this will result in the cheesecake cracking.
Add eggnog, sour cream, flour, and vanilla to the cream cheese and mix until just combined.
Add eggs, one at a time, and beat until just incorporated.
Pour cheesecake batter into the springform, and carefully bang the pan on the countertop, to release trapped air bubbles from the batter.
Place springform in the 10" cake pan, and place both pans into the roasting pan.
Very carefully, add warm water to the roasting pan, until it goes halfway up the cake pan. Don't splash water onto the cheesecake batter.
Carefully place roasting pan in the oven, and bake cheesecake for 1 1/2 hours(90 mins.).
When the cheesecake is finished baking, turn the oven off and leave cheesecake in the oven for 1 hour. This allows the cheesecake to cool with the oven and helps to prevent cracking.
After the hour, remove the cheesecake from the oven and run a butter knife around the edges of the cheesecake.
Allow to cool at room temp. for an additional 2+ hours, then place in the refrigerator for at least 4 hours(I refrigerate overnight).
Once the cheesecake is set, serve topped with whipped topping and nutmeg, and enjoy!