Line two muffin pans with paper cupcake liners. (Alternatively, spray with cooking spray.)
In a medium sized bowl, sift together the flour, baking soda, and salt.
In another bowl, mash the bananas with a fork. Add the milk and yogurt, and set aside.
Using a stand mixer on medium speed, combine the butter (or pureed avocado) and sugar (for about 2 minutes) until the mixture achieves a light and fluffy consistency. Next, add eggs and vanilla. Stir in the flour mixture and then, add the banana-yogurt blend.
Divide batter into 24 muffins cups.
Bake at 350 degrees for about 25 minutes until the muffin tops are golden brown. Insert a toothpick in the center of a muffin. If it comes out clean, everything’s ready.
Carefully remove the muffins and cool on a wire rack.