A note about substitutions: You can substitute casein powder for the whey powder. For a dairy-free/vegan version, you could use a chocolate pea protein blend in the fudge, and omit the protein powder in the peanut butter swirl. Other vegan powders are chalkier, and wouldn't work well. You could also use 2 tablespoons of peanut butter in place of the powdered peanut butter (and then half the amount of water).