Prep: Heat oven to 375° F and spray or line a mini muffin tin.
Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
Wet Ingredients: In a large bowl, with a hand mixer, mix the avocado until smooth and creamy. Add in the maple syrup and oil (or butter) and mix well. Add in the egg, milk, and vanilla extract and mix until completely combined.
Combine: Pour the flour mixture into wet ingredients. Gently fold the ingredients together until just combined. Do not overmix.
Add Blueberries: Gently fold in the blueberries.
Fill: Spoon the batter into the muffin tin, filling 3/4 way to the top.
Bake: Place the muffin pan into the oven for 12-15 minutes or until just golden.
Cool: Let cool in the pan for 5 minutes before transitioning the muffins onto a cooling rack. Serve and enjoy!