Mix milk and protein powder (in a shaker or blender).
Pour into ice cream maker. Add cacao nibs once the ice cream is done churning.
Or, add cacao nibs and pour into a container. Freeze for several hours, stirring every half hour or so.
Notes
A note about substitutions: You can use any type of milk. If not whey, I would recommend casein or pea protein, as long as you enjoy it as a shake. Note that the scoops for this protein powder are smaller, and this would be 1.5 scoops of most other protein powders.