Make the chia egg by mixing together 1 Tbsp ground chia seeds and 3 Tbsp of water. Set aside.
Grind 100g of oats into flour.
Place the rest of the oats in a large bowl. Add oat flour, salt, baking powder and the chocolate chips (reserving about 1 Tbsp on the side).
Mash the bananas with a fork. Add vanilla extract, melted coconut oil, maple syrup and chia egg.
With a wooden spoon, mix the ingredients together carefully until they are all well blended.
Line a baking tray with greaseproof paper. Scoop out cookie mix 1 tablespoon at a time and place on the baking tray. Flatten to around 1 cm [0.4 inches] each cookie, to make them round and even.
Add some of the reserved chocolate chips on top of each cookie.
Place in the oven for 12-15 mins until cooked.
Once cooked, leave to cool down on a grid.
These cookies will keep for a few days in an airtight container.