Line a large baking sheet with parchment paper or a silicone baking mat.
In a medium mixing bowl, stir together oats, whole wheat flour, baking powder, cinnamon and salt until combined. Set aside.
In a large mixing bowl, mash banana. Add butter and mash together. Next add egg, brown sugar, maple syrup and vanilla extract, and beat on medium-high with a mixer until well combined, at least 3 minutes, stopping to scrape down the bowl as needed.
Add wet ingredients into dry ingredients. Mix on a low speed until flour dissolves. If you are mixing in chocolate chips or sprinkles, add up to 3/4 cup of the mix and fold in gently with a rubber spatula.
Cover the bowl and place in fridge for 30 minutes.
After 30 minutes, remove from fridge and preheat oven to 350 degrees.
With a large cookie scoop, scoop dough onto prepared baking sheet. My cookie scoop yielded almost 2 tablespoons or so per scoop. This yields about 10-12 cookies.
With back of a spoon, gently press each ball dough to flatten a bit. They will spread out as they bake.
Place in oven for about 15 minutes. Remove and let cookies cool before handling them.
Once cooled, top with about a 1/2 tablespoon of Nutella per cookie. Spread Nutella over the cookie with the back of a spoon. Yum!