Add the ingredients to the Ninja Creami container and stir to combine.
Freeze on a level surface for at least 24 hours.
Remove from the freezer and process on the ice cream setting. If needed, respin.
Notes
I've found that if you respin this one too much, it definitely softens. If adding mix-ins, I typically do it after just processing once. Otherwise I have to stick it back in the freezer to harden up again.
I usually run a little warm water along the outer edge of the container for 30 seconds before processing to allow the very outer layer to thaw.
If you have leftovers, simply smooth out the top and return to the freezer.