EZ - whatever flavor (or nonflavored) whey protein you like, in the blender w/ water, ice & 1-2 tbsp peanut butter. I'm thinkign the processing they would have to do to make a peanut butter that is still spreadable & not clumpy with whey in it would just get to be too big a deal. Plus there's already lots of peanut butter flavored whey protein (e.g. One Way bars, protein mix etc.