These peanut butter oat muffins make the perfect healthy and filling snack or breakfast. Use whole oats opposed to quick cooking oats in this recipe. Make sure to stir the all-natural peanut butter before measuring in order to mix in all the natural oils that tend to separate in the all-natural brands. Also, warm peanut butter slightly in the microwave for 30 seconds in order to make it easier to measure and mix. Feel free to use a peanut butter substitute if allergic to standard peanut butter. This recipe can be made using a flax egg or normal egg [for non-vegans]. Leave muffins to cool fully before taking them out of the muffin tin.