Whisk whole-wheat flour, all purpose flour, baking powder, cinnamon, baking soda and salt in a medium bowl.
Mash one banana in a large bowl. Add egg, Green Mountain Creamery Maple Greek Yogurt, water and ¼ cup oil to the mashed banana and stir to combine. Stir the dry mix into the wet mix until completely moistened.
Preheat griddle over medium-high heat. Brush with 1 teaspoon oil. Preheat oven to 300 degrees F.
Ladle 1/3 generous cup batter at a time out onto griddle, spreading batter to 4-5 inch rounds and spacing evenly. Let pancake cook until dry around the edges, and bubbles on top start to burst, 2 to 3 minutes. Carefully flip over, and continue cooking until cooked through (the center will no longer feel liquid when gently pressed down.) Keep the pancakes warm in oven on a baking sheet or wire rack.
Repeat oiling the griddle with the remaining teaspoon oil and the remaining half of the batter, adjusting heat to low as necessary to prevent too much browning.
Slice the remaining 2 bananas. Serve pancakes topped with the sliced bananas, walnuts and maple syrup on top.