Use natural peanut butter. The kind with one ingredient on the label: peanuts (and salt if you like, but make sure to cut the added salt in the recipe if so). I tested this recipe using both Trader Joe's and Whole Foods store brands. Both worked great! Any brand that is just peanuts and salt will do. I haven't tested this using conventional, shelf-stable peanut butter so I can't guarantee the same results. Also, room temperature peanut butter is best for mixing. I usually just open a fresh jar to make this recipe because it uses most of a standard 16 oz jar.