Heat waffle iron on high heat, about one notch down from the highest setting. Preheat oven to 250 degrees Fahrenheit.
In a medium bowl, whisk together the flour, sugar, baking powder, sea salt and nutmeg. Stir in the chopped walnuts.
In a microwave-safe bowl, combine the melted coconut oil and milk. Microwave for 30 seconds, or until the mixture is lukewarm. Whisk in mashed banana, egg, and vanilla extract.
Add wet ingredients to dry ingredients and stir until just combined. Be careful not to over mix. Tiny lumps may remain. Pour batter onto the heated waffle iron, enough to cover the center and most of the central surface area. Once the iron has stopped steaming and the waffle is deeply golden, transfer it to a cooling rack or baking sheet. Don’t stack your waffles on top of each other, or they’ll lose crispness. Place in oven to keep warm. Repeat. 5 minutes
Top with sliced bananas and 100% pure maple syrup, and serve. Save leftovers in the fridge and reheat by placing the waffle back in the griddle or in the toaster on a light setting.