Make the maple-honey syrup: in a small saucepan combine 1/2 cup maple syrup, 1/2 cup honey, and 3 tablespoons butter; warm over low heat just until the butter melts and the mixture is liquefied. Keep warm or transfer to a heatproof bowl and cover.
Prepare the waffle iron by spraying it with nonstick spray and preheating to medium-high or following the manufacturer's instructions.
In a medium bowl whisk together 1 cup flour, 1 1/2 tablespoons granulated sugar, 1 teaspoon baking powder, 1/4 teaspoon baking soda, and 1/4 teaspoon salt.
In another bowl whisk together 1 cup sour cream, the mashed medium ripe banana, the beaten large egg, 1/2 cup milk, and the 1/4 cup melted unsalted butter until combined.
Make a well in the dry ingredients and pour in the banana-sour cream mixture; fold gently with a rubber spatula just until the batter is evenly moistened. Do not overmix.
For each waffle, pour about 3/4 cup batter onto the preheated waffle iron, close the lid, and cook until crisp and well browned, about 4 to 5 minutes per waffle.
Remove waffles from the iron with a fork, serve immediately, and drizzle with the warm maple-honey syrup.