Preheat oven to 350 degrees. Sift together the flour, baking soda, salt, cinnamon, nutmeg, and walnuts. Set aside.
In a large bowl using an electric mixer, cream the butter and sugar. Add eggs, one at a time, mixing until well blended. Mix in the mashed bananas, extract and milk and mix until well blended.
Stir in the dry ingredients to wet, folding until just mixed. Be sure you don't over mix the muffin batter.!Scoop batter with a large cookie scoop and place in a 12 cup muffin tin that has been lined with paper liners. Bake for 25 minutes or use the toothpick test and if the toothpick comes out of the muffin clean its ready. Remove from the oven.
To make the icing mix the powdered sugar, maple syrup and half and half together. Drizzle over top of the muffins after they have slightly cooled.