01 - Preheat the oven to 350°F. Lightly grease a 9x9 inch baking dish with cooking spray or butter.
02 - In a large bowl, whisk together the mashed bananas, eggs, Greek yogurt, honey, almond milk, and vanilla extract until smooth and well combined.
03 - In a separate medium bowl, combine the rolled oats, protein powder, baking powder, cinnamon, and salt. Mix thoroughly to distribute evenly.
04 - Add the dry ingredients to the wet mixture and stir with a spatula until just combined. Do not overmix.
05 - Gently fold in the blueberries, being careful not to crush them.
06 - Pour the batter into the prepared baking dish, spreading evenly. Sprinkle with chopped nuts and chia seeds if desired.
07 - Bake for 35 to 40 minutes, or until the top is golden brown and a toothpick inserted in the center comes out mostly clean.
08 - Let the bake cool for 10 minutes before slicing into squares. Serve warm or at room temperature.