Preheat the oven to 375°F.
Spray an 8x8 square baking dish with cooking spray.
In a large bowl, mix together the oats, almond milk, cocoa powder, maple syrup, baking powder, sea salt, flaxseed, mashed banana, coconut oil, peanut butter and vanilla. Stir together, then add 1/8 cup of the chopped chocolate.
Carefully pour oatmeal mixture into the prepared baking dish.
Scatter remaining chocolate on top.
Bake for 25-30 minutes, or until the oatmeal has set. Remove from the oven and let cool for a few minutes. Portion and serve with a drizzle of peanut butter on top.
For storage: store in the refrigerator in an airtight container for 4-6 days.
To reheat: To reheat the whole baked oatmeal, cover with foil and reheat in a 350°F oven for about 20 minutes. For individual portions, set toaster oven to 350°F and bake for 5-10 minutes or reheat in the microwave for 1 minute.