Preheat the oven to 350 degrees F.
Grease a muffin tin or line it with paper liners.
In a large bowl, whisk together flour, baking powder, baking soda, and salt.
In another bowl, mash the bananas and stir in milk, oil, and egg. (Whisk it for 5-10 mins for better results).
Add wet ingredients to dry ingredients and mix until just blended.
Gently fold in blueberries.
Fill muffin cups about two-thirds full and bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Let cool slightly before serving. Enjoy!