Preheat oven to 350°. Melt butter in microwave for 30-60 seconds until melted. In the meantime, mash overripe bananas until well mashed in a large mixing bowl.
In the bowl of mashed bananas, add salt and baking soda and stir to combine. Mix in melted butter.
Add sugar, milk, vanilla extract and egg. Stir until combined.
Add flour and stir to combine. Note: If you would like the batter to be a bit more moist, add an additional tablespoon of milk and stir.
Pour batter into greased muffin pans. Bake for 20 minutes or until toothpick comes out clean.
Notes
For egg allergies, substitute one egg for 1/4 cup of vegetable oil or 1/4 cup of unsweetened apple sauce. This batter yields 12-16 muffins.You may also bake this batter in a 9x5 loaf pan. Bake for 50 minutes or until toothpick comes out clean.