Preheat oven to 300 degrees. Line an 8x8 pan with foil and spray with a non-stick spray. Make sure the foil folds over the sides of the pan.
In a food processor, pulse the Oreos until finely crushed. Add in the butter and pulse again until well combined. Spread the mixture onto the bottom of your prepared pan and set aside.
Wipe out the food processor and add the cream cheese and sugar. Pulse until nice and creamy, leaving no lumps behind. Add in the flour, eggnog and egg, pulsing until well combined. Fold in the chocolate chips and pour the mixture onto the crust layer in your pan. Sprinkle a few chocolate chips on top for appearance.
Bake for 35-40 minutes, just until edges are set. Cool completely on the counter. Then move to the fridge for a few hours to chill.
When ready to serve, remove the bars from the pan by lifting the foil. Sprinkle the nutmeg on top. Store in the refrigerator.