Preheat your oven to 350°F and lightly grease a 12-slot mini-muffin tin with coconut oil spray.
In a large mixing bowl, mash the banana with a fork until it reaches a smooth consistency with no large lumps.
Whisk in the egg whites until well combined, then add the chocolate protein powder, cacao powder, oat flour, baking powder, sea salt, and cinnamon.
Stir the batter vigorously until all dry ingredients are fully incorporated and the mixture is dark and glossy.
In a separate small bowl, stir the Greek yogurt and almond butter together until the mixture is uniform and creamy.
Spoon the brownie batter into the prepared muffin tin, filling each slot about three-quarters of the way to the top.
Place a small dollop of the yogurt-almond mixture onto the center of each brownie bite.
Use a toothpick to gently swirl the yogurt mixture into the brownie batter to create a marbled pattern.
Bake for 12 to 14 minutes until the bites are set and a toothpick inserted into the center comes out clean.
Let the bites cool in the pan for at least 5 minutes before removing them to a wire rack to finish cooling.