In a medium bowl, mash enough bananas to equal 1 cup.
Add to the mashed bananas; milk, egg, vegetable oil, vinegar, and vanilla. Mix well to combine
In a separate bowl, combine flour, sugar, baking powder, baking soda, cinnamon, nutmeg, and salt. Mix well.
Add the dry ingredients to the banana mixture, stirring to combine. Let the batter rest for 5 to 10 minutes. You should start to see bubbles forming as the vinegar reacts to the baking soda.
Meanwhile, preheat the griddle to 325° F. **If you're using a stovetop, lightly butter the pan, start with your burner on medium, and adjust as needed for a golden-brown pancake.
Using a ⅓ cup measuring cup, scoop the pancake batter and pour it onto the griddle. Allow the batter to cook for about 1 ½ to 2 minutes, or until the first side is golden brown. Flip the pancake and cook for an additional 1 ½ to 2 minutes, or until it is golden brown. Cooking times may vary depending on your cooking surface. The best indicator is an even golden-brown pancake. If you are still uncertain, cut one pancake in half to check that it is cooked through to the center.
Serve warm with butter and maple syrup. Add chopped walnuts to complete the dish.