Preheat oven to 350°F (180°C) and fold a 7x7 in (15 cm x 15 cm) brownie pan with parchment paper.
In a large mixing bowl, mash the banana. Add egg, maple syrup, nut butter, vanilla extract and a pinch of salt. Using a whisk or fork, mix until the batter reaches a smooth consistency.
Add to the wet mixture protein powder, almond flour and cocoa powder. Stir until dry and wet ingredients are combined and free of lumps - do not overmix.
Transfer the batter into the prepared baking pan and top with chocolate chips if desired.
Bake in hot oven for around 18 to 20 minutes, or until they are no more raw inside. Make sure you do not bake them for too long, or the brownies will get dry.
Let cool completely at room temperature before slicing.