Preheat oven to 180C fan settings. Make chia (or flex) egg by combining ground chia (or flax) 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 6 pecans for topping and add the rest. Mix to combine.
In a separate smaller mixing bowl, combine wet ingredients: chia egg, almond milk, melted coconut oil, vanilla extract. Mix to combine.
Add mashed banana to dry bowl, then pour in wet ingredients and stir to combine.
Reserve a handful of blueberries for topping, and add the remaining to the bottom of your baking dish (I use a 22x15 cm baking dish). Slowly pour oatmeal mixture over and spread evenly. Top oatmeal bake with reserved blueberries and pecans. Push the blueberries and pecans you put on top into the batter with your fingers, so they don't just sit on the top!
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.