Preheat the oven to 180°C (350°F) and grease two 150 ml (5 oz.) ramekins with oil or butter. Set aside. I recommend placing the ramekins on a baking sheet or in a baking container of some kind for easier removal from the oven after baking.
Add the banana, egg, maple syrup, oil, vanilla, oats, baking powder, and salt to a blender or blending container in that order. (If using a bullet blender, reverse the order - you want the wet ingredients to be in contact with the blade first.)
1 large overripe banana, 1 large egg, 1 tablespoon maple syrup, 1 tablespoon oil, 1 teaspoon vanilla extract, 45 grams (½ cup) rolled oats, ½ teaspoon baking powder, ¼ teaspoon sea salt
Mix on high speed until very smooth and the oats have broken down. It should look like muffin or pancake batter. Stir in any mix-ins now if using.
Divide the batter equally between the two prepared ramekins, using a spatula to scrape any additional batter out of the container if needed.
Bake for 20 to 22 minutes, or until lightly golden and just firm when touched. Cool for at least five minutes before serving, handling the hot ramekins carefully.
Notes
Optionally mix in a couple tablespoons of mini chocolate chips, chopped chocolate, blueberries, chopped nuts or seeds, or raisins after blending. Spices (½ teaspoon cinnamon, ¼ teaspoon any other sweet spice) should be added with the other dry ingredients.If you want to make one larger portion of baked oats instead of two, use a 230 ml (8 oz.) ramekin and bake for 24 to 26 minutes instead.Baked oats don't freeze well, but can be kept at room temperature for a couple hours before serving. Cool before covering tightly or placing in a sealed container and serve at room temperature or refrigerate for up to a day.