In a blender or food processor, combine cashews, water, agave, peppermint flavoring, and spinach. Process until smooth.
Add whey protein. Process until smooth.
Pour into a bowl, and fold in cacao nibs.
Cover the bowl and freeze for about 4 hours. Every half hour or so, take the bowl from the freezer and mix the ice cream. (Other options are to use an ice cream maker, or use the ice and salt method.)
Enjoy!
Notes
A note about substitutions: you could substitute greek yogurt for the soaked cashews (but then it'll taste like yogurt). You could also substitute casein protein for the whey. For a paleo version, replace the agave with your preferred paleo sweetener.