Preheat oven to 400 degrees F. In a small bowl mix 1 tbsp chia seeds or ground flax. Add 3 tbsp aquafaba (the water from a fan of chick peas) or plain water. Set aside to gel for 10 mins.
Combine flour, oats, sugar, baking powder, baking soda and salt
In a large bowl, pour in flax egg. Stir in milk, oil and vanilla. Add the mashed banana and combine thoroughly
Stir the flour mixture into the banana mixture until just combined
Mix in chocolate chips
Line a 12 cup muffin tin with paper baking cups and divide batter among them