Preheat oven 350 degrees F.
Lightly spray a muffin pan with oil.
In a medium bowl, whisk together the smashed bananas, milk and vanilla.
In another bowl, combine the oats, flax, baking powder, salt and cinnamon.
Pour the dry ingredients into the wet and stir until well combined.
Stir in the strawberries and chocolate chips (if using).
Fill the muffin tins to the top with the oatmeal mixture and press down gently to make them compact.
Bake for 20-25 minutes until the edges are golden brown and the oatmeal is baked through.
Let cool in the pan on a wire rack for at least 10 minutes before serving. Any leftovers can be refrigerated.