Pre-heat the oven to 350º F.
Line a 12-cup muffin tin with paper liners.
Pour 2 cups of whole rolled oats into a food processor and grind until it's a fine powder. About one minute should do it.
Mix the dry ingredients (ground rolled oats, whole rolled oats, baking soda, baking powder, cinnamon, salt) in a bowl.
Mash 3 1/2 to 4 medium to large overripe bananas in a bowl (about 420 grams of banana, but don't worry about exact weight).
Mix the wet ingredients (mashed banana, peanut butter, applesauce, vanilla extract, apple cider vinegar, coconut oil, chai seeds) in a bowl.
Combine all of the ingredients and mix. I like using a rubber spatula to get the batter off the sides of the bowl. The batter should be liquid enough to pour.
Evenly distribute the batter into the 12 muffin liners. Fill each cup about 3/4 of the way, and distribute the remaining batter as evenly as possible. Feel free to lick the spatula when finished.
Bake at 350ºF for 20 minutes or until a knife comes out clean.
Take them out and let them cool for a least 10 minutes in the tin. After 10 minutes, transfer each muffin to a cooling rack with the liners still on.
Store in a closed container in the fridge for up to a week. Even better, store in a closed container in the freezer, and take a muffin or two out each night and put them in the fridge so they are ready to enjoy the following day.