Blend the base: Add the milk, protein powder, sweetener, xanthan gum, and salt to the Ninja Creami pint. Blend for about 30–60 seconds until completely smooth, making sure no clumps remain. I recommend an immersion blender, but a regular blender, handheld milk frother, or shaker cup can also work. Do not add the Kit Kat Miniatures yet.
Prepare the Kit Kat: Freeze one whole Kit Kat Miniature separately for the Mix-In cycle. Reserve the remaining two Kit Kat Miniatures for topping.
Freeze: Make sure the liquid mixture is below the MAX FILL line. Place the pint on a level surface and freeze for at least 24 hours. Freeze with the lid removed to help prevent a bump from forming.
Prepare to spin: Remove the pint from the freezer and make sure the frozen surface is level, with no raised bump. Do not process a pint with a significantly uneven frozen surface. If necessary, allow the mixture to soften or melt, smooth it out, and refreeze it on a level surface until completely solid. Run hot water over the outside of the pint for about 1 minute or let it sit on the counter for about 15 minutes.
Spin: Process using the Lite Ice Cream setting.
Assess the texture: After the Lite Ice Cream cycle, check the texture. If it still needs significant processing, run a Re-Spin. If it’s already close to the texture you like, you can skip the Re-Spin and run the Mix-In cycle instead, whether or not you’re actually adding mix-ins.
Add mix-ins and enjoy: Make an off-center hole with a butter knife, add the whole frozen Kit Kat Miniature, and run the Mix-In cycle. Chop the remaining two Kit Kat Miniatures and add them on top after processing. Enjoy!