Preheat the oven to 350°F (180°C) fan on.
Prepare the batter: this recipe yields 3 servings, each prepared in an individual oven-safe container. The ones I used are 600ml / 20oz (15 cm x 15 cm x 6 cm). In each container, place 50g of banana and mash it with a fork until smooth. Evenly divide and add the oats, chia seeds, cinnamon, protein powder, baking powder, blueberries, lemon zest, and milk among the three containers. Stir each well to combine all ingredients. Let the mixtures sit for 10 minutes to allow the chia seeds to bloom and thicken the batter. Optionally, sprinkle some extra blueberries at the top of the batter.
Bake: Place the containers on a baking sheet for easier handling and bake in the preheated oven on the middle rack for 30 minutes.
Serve: Once the baked oats are done, remove them from the oven and let them cool slightly. Enjoy hot or cold, as is, or drizzle some yogurt, fresh berries, or maple syrup.
