Preheat oven to 350F/176C. Make chia egg by combining ground chia with water. Stir well to combine and let sit at least 5 mins.
In a large mixing bowl combine oats, coconut sugar, cinnamon, nutmeg, cardamom, baking powder and sea salt. Reserve 2 tbsp pecans for topping and add the rest. Mix to combine.
In a separate smaller mixing bowl, combine wet ingredients: chia egg, almond milk, maple syrup, melted coconut oil, vanilla extract. Mix to combine.
Add mashed banana to dry bowl, then pour in wet ingredients and stir to combine.
Reserve 1/2 cup blueberries for topping, and add the remaining to the bottom of your baking dish (I used a square 8.5x8.5 inch baking dish). Slowly pour oatmeal mixture overtop and spread to even. Top oatmeal bake with 1/2 cup reserved blueberries, and 2 tbsp reserved pecans. (Optional to also top with sliced banana if you have, but not necessary).
Bake oatmeal for 40-50 minutes or until golden and firm. Let cool for at least 15 minutes to set. Then cut in squares and serve. (I like to serve with coconut yogurt, fresh banana and maple syrup).