Preheat oven to 350 degrees and lightly grease a muffin pan or use liners. Set aside. 

In a large mixing bowl combine oats, baking powder, cinnamon, salt, and chia seeds. 

In another bowl combine mashed bananas, almond milk, maple syrup, coconut oil, and vanilla. 

Pour banana mixture into oat mixture and stir to thoroughly combine. 

Scoop mixture into muffin wells and smooth the tops. 

Top with banana slice and press down on it lightly if using. 

Bake for 25 minutes or until edges are lightly browned and the tops are dry. 

Cool for 5 minutes before removing from muffin pan. 

Store in the fridge or the freezer for longer term storage. 

To serve reheat briefly in the microwave or oven. Drizzle with maple syrup, if desired.