Mash the banana: Peel 1 large ripe banana and place it in a medium bowl. Mash it well with a fork until mostly smooth.
Mix the wet ingredients: Add 1 cup Greek yogurt, 1 cup milk, 2 teaspoons honey (or maple syrup), and 1 teaspoon cinnamon to the bowl. Whisk until smooth and well combined.
Add the oats and chill: Add 1 cup rolled oats. Stir until all the oats are coated. Cover the bowl or divide the mixture into two jars. Refrigerate for at least 6 hours, or overnight.
Serve: Stir well before eating. Serve straight from the fridge, or warm gently in the microwave for 30 seconds to 1 minute if you prefer them warm. Top with nuts, fresh fruit or an extra drizzle of honey if you like.
