Preheat the oven to 375-degrees F. Grease a jumbo muffin tin using coconut oil.
In a large bowl, combine all the dry ingredients, except brown sugar, and whisk together. Set aside.
¾ cup all-purpose flour, 1 cup whole-wheat flour, ⅔ cup quick cooking oats, ½ teaspoon salt, 2 teaspoon baking powder, 2 tablespoon ground flax seed, 2 tablespoon wheat germ, 1 teaspoon ground cinnamon
In the bowl of an electric mixer fitted with a paddle attachment, beat the mashed banana, butter, peanut butter, brown sugar, and eggs together until fluffy. Add the milk and vanilla and mix to combine.
1 banana, 2 tablespoon butter, ⅔ cup natural peanut butter, 1 cup brown sugar, 2 large eggs, 1 teaspoon vanilla extract, ¾ cup milk
Slowly add the dry mixture a little at a time until just blended. Stir in the mini semi-sweet chocolate chips.
1½ cups mini semi-sweet chocolate chips
Fill the prepared muffin tin two-thirds of the way full. Bake for 18-20 minutes – a toothpick inserted into the middle should come out slightly sticky. Let the pan set for 5 minutes before turning the muffins out onto a rack to cool.
Store peanut butter muffins in an airtight container or individual zipped bags.