Preheat oven to 350F.
In one bowl, cream mashed banana with maple syrup, vanilla, coconut oil, and butter.
Add the eggs and whisk well.
In a separate mixing bowl, combine all the dry ingredients together.
Take your dry ingredient bowl and pour a little bit at a time into the mashed banana egg bowl, alternating with splashes of milk and stir to combine.
Repeat until all dry ingredients are mixed in. If mixture seems like it's too wet you can stop adding milk. If it seems dry, add more milk.
Add the blueberries last and stir to evenly distribute.
Grease tin with a little bit of coconut oil if it's not nonstick. Spoon batter into the muffin tin, filling to just below the rim.
Bake for approximately 22-28 minutes. Check with a toothpick in the center.