Preheat your oven to 350 degrees F. Spray a muffin tin with non-stick cooking spray or fill with muffin liners. In a large mixing bowl, combine mashed bananas (I mashed via my blender) with eggs, yogurt, coconut oil, maple syrup, vanilla and sugar (if using). Stir vigorously for about a one minute, or until the mixture is smooth. In a separate bowl, combine the dry ingredients. For best results, spoon flour into cup (rather than scooping with cup) and then level using a butter knife. Make a well in the center of the flour mixture and add wet ingredients. Gently stir until just combined. Don't overmix.Spoon batter into the prepared muffin tins filling each one completely full and top with chopped nuts. Bake for about 25 minutes or until a toothpick comes out clean.Cool for about five minutes then remove to a wire rack to finish cooling. Because these muffins are so moist, they have a tendency to stick to muffin liners, use a butter knife around the edges to remove. Enjoy!