Preheat griddle to medium heat (350 degrees).
To a large mixing bowl add flour, baking powder, sugar, and salt. Use a whisk to combine.
Peel the bananas and place in a separate bowl. Use a fork to mash until smooth (no big lumps).
Add egg, milk, water, and vanilla extract to the mashed banana. Whisk until well combined.
Melt 3 Tablespoons of butter in a small container and set aside. (Make sure the butter is not steaming hot so that it won't cook the eggs)
Make a well in the center of the dry ingredients.
Pour the banana mixture into the well, then pour the melted butter into the well.
Stir ingredients together gently until just combined. Batter should be thick and lumpy, but no dry patches.
Melt a little butter on the hot griddle and use a spatula to spread it across the surface.
Scoop out 1/4 cup of batter for each pancake and cook on the griddle about 2-4 minutes, until bubbles start to form and pop on the surface.
Carefully flip pancakes and cook another 1-3 minutes, until both sides are golden brown and pancakes are cooked through. Remove from griddle.
Serve pancakes warm with sliced bananas (optional), chopped walnuts (optional), butter and syrup. Enjoy!