Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe ramekin or baking dish.
Place the rolled oats into a high-speed blender and pulse until they reach a fine, flour-like consistency.
In a medium mixing bowl, mash the banana until smooth, then stir in the Greek yogurt, vanilla extract, cinnamon, sea salt, baking powder, and chia seeds.
In a separate clean glass or metal bowl, use a hand mixer to beat the liquid egg whites until stiff peaks form.
Incorporate the blended oat flour into the banana and yogurt mixture until fully combined.
Gently fold the whipped egg whites into the batter in two stages using a spatula, taking care not to deflate the air bubbles.
Transfer the mixture into the prepared ramekin and bake for 22-25 minutes until the center is set and the top has puffed up beautifully.
Serve immediately while warm to enjoy the delicate, cloud-like texture.