01 - Preheat oven to 350°F. Lightly grease a 9x9-inch baking dish.
02 - Toast oats and sliced almonds in a dry skillet over medium heat for 3 to 4 minutes, stirring frequently until fragrant and lightly golden. Remove from heat.
03 - In a large mixing bowl, combine toasted oats, almonds, chopped walnuts if using, ground cinnamon, salt, and baking powder.
04 - In a separate bowl, whisk together milk, eggs, maple syrup or honey, melted butter or coconut oil, and vanilla extract until smooth.
05 - Pour wet mixture into dry ingredients and stir until well combined.
06 - Gently fold blueberries and sliced banana into the combined mixture.
07 - Pour mixture evenly into prepared baking dish and bake for 35 minutes or until set and golden on top.
08 - Allow to cool for 5 minutes before serving. Serve warm, optionally with yogurt or extra maple syrup.