Preheat oven to 350 degrees.
Prepare your muffin tins. I swear by using silicone muffin liners. I also use Pam with Flour so that you don’t need muffin liners at all.
Beat the butter & sugar on medium-high speed until light and fluffy – about 2-3 minutes.
Beat in eggs, buttermilk and vanilla.
Beat in bananas.
Gradually add in flour, baking powder, baking soda, and salt at low speed.
Add blueberries and gently stir.
Spoon the batter into your muffin tins.
Bake for 15 minutes for mini muffins or 20-25 minutes for regular sized muffins.