Preheat the oven to 350º F. Line and spray the muffin pan with non-stick cooking spray and cupcake liners. This recipe makes 12 muffins.
Combine the oats, flour, baking powder, and salt in a mixing bowl and stir to mix. Set aside.
In a mixing bowl of your stand mixer fitted with the paddle, beat together the sugar and the butter. Beat for about 5 minutes until it is light and fluffy.
On low add in the sugar, buttermilk, and oil.
Add in the eggs one at a time, mashed bananas, and mix to combine. The batter will look terrible, very chunky, and that it is curdled dairy products but once you add the dry ingredient it looks normal.
Slowly add the flour mixture to the wet mixture. Mix until combined, then add in the walnuts or chocolate chips.
Scoop out the batter to fill each cup in your muffin pan. I used a large ice cream scoop for this, which is about a 1/3 cup size.
Bake for25 to 30 minutes, until golden brown and the tops of the muffins, spring back when touched. Remove from the oven and let cool slightly.
