In a high-speed blender, combine the old-fashioned rolled oats, large egg, over-ripe banana, nut butter, almond milk, vanilla extract, baking powder, and ground cinnamon. Blend on high for 20-40 seconds until smooth and creamy.

Once blended, transfer the mixture to a mixing bowl and fold in your choice of mix-ins like chocolate chips or blueberries.

Pour the batter into a greased microwave-safe ramekin or mug, leaving a little space at the top.

Place the ramekin in the microwave and cook on high for 90-120 seconds. Check for doneness after 90 seconds; continue microwaving in 10-second increments if needed.

Carefully remove the ramekin from the microwave, allow to cool for a minute, then top with peanut butter, yogurt, or any preferred toppings.