Preheat the oven to 180C/350F.
Add the chia seeds to the milk and allow it to stand for 15- 20 minutes while your oven preheats. You can do this a little in advance of starting the recipe. This allows for the chia seeds to soften and absorb some of the moisture.
Add the wet ingredients: mashed banana, egg peanut butter, milk, and vanilla to a bowl or jug and mix to combine.
In a large bowl add the rest of the ingredients (dry) and give it a mix.
Add the wet ingredients to the dry ingredients and mix.
Grease or line a 20cm x 20cm (8 X 8 inch) square baking dish with non-stick parchment paper. Decant the mixture into the tin, pressing it into the corners to level it.
Bake for 25 – 30 minutes until golden brown and firm to the touch throughout.
Allow to cool then remove and cut out 6 - 9 pieces depending on your portion size. Store in the fridge for a week and reheat what you need in the morning for breakfast as needed.
Any leftovers can be frozen for future use.
Serve with yoghurt, milk, fresh berries, maple syrup, honey, fresh berries, sliced bananas or anything else you fancy.