Place the butter and ice cream on your kitchen counter and let it sit for 30 minutes until softened.
Unwrap the butter sticks and put them in a large mixing bowl. Pour the sugars on top, then cream together with a hand mixer until well blended. Add the cinnamon, nutmeg, salt, and ice cream. Mix well.
Transfer to freezer-safe mason jars or ice cube trays* and freeze.
Notes
To use for Hot Buttered Rum: In a medium-sized mug, combine 2 tablespoons of mix with 8 ounces boiling water. Add in 1 1/2 ounces of rum. Sprinkle with cinnamon.*Ice cube trays are super handy for portioning out 1 serving of mix at a time. If you want to use this method, place the filled ice cube trays in the freezer; once frozen, pop them out and store them in a freezer zipper bag.