Heat oven to 350°F. Lightly grease 8x8-inch pan. Mash bananas with a fork until slightly chunky. Stir together water, egg, banana, and ⅓ cup walnuts, and muffin mix until blended.
Spoon batter into lightly greased pan and spread evenly. Light swirl in half of the cinnamon toppings into batter. Sprinkle remaining batter and ⅓ cup of walnut evenly over batter
Bake for 40-45 minutes or until toothpick inserted into center comes out clean. For glass pan, add 5 minutes to bake time. Cool 5-10 minutes before cutting.