In a wide mouth jar (12-16 oz.) add oats, yogurt, milk, mashed banana, chia seeds, nuts, syrup, vanilla and cinnamon.
Mix together until fully combined.
Cover with a lid and refrigerate for at least 4 hours or overnight.
Garnish with extra sliced banana, nuts, a sprinkle of cinnamon or a drizzle of syrup.
Notes
Choosing bananas: I recommend choosing a ripe banana for this recipe, but not too ripe (not the super brown ones like banana bread). Go for a nice golden yellow banana with some spottiness. It shouldn't have any green.