Preheat oven to 350° F. Grease a standard muffin pan or line with baking cups.
In a large bowl, whisk together the flour, baking soda, salt, and cinnamon.
In a medium bowl, stir together the mashed bananas, sugars, butter, milk and egg.
Add the wet ingredients to the dry ingredients and stir to combine.
Fold in half the chopped walnuts until combined.
Divide the batter evenly among the muffin cups. Sprinkle the remaining walnuts over the tops of the muffins.
Bake 22-24 minutes, or until the tops of the muffins are brown and a wooden pick inserted into the center comes out clean.
Cool in the pan for 10 minutes, then transfer the muffins to a wire rack to cool completely.
Notes
Use overripe bananas, with brown spots on the peels, for these muffins. Bananas that are under ripe won’t add enough moisture to the muffins.
Remember to use the “spoon and level” method when measuring your flour. Use a spoon to scoop the flour into the measuring cup and level off the top with the back of a table knife. Scooping the flour with the measuring cup can give you more flour than needed.
Use a large scoop to fill the muffin cups with batter. This will keep the muffins similar in size and ensure even baking time.
After cooling the muffins for 10 minutes, remove them to a wire rack to finish cooling. Leaving the muffins in the pan to finish cooling will make the bottoms of the muffins soggy.