Stir the almond butter, chia seeds, milk, cinnamon, vanilla extract, and 1/2 the banana (mashed) together in a jar or container with a lid (or blend in a blender). Once smooth, stir in the oats. Cover and let sit in the refrigerator overnight.
In the morning, slice the remaining half of the banana and stir into the oats. Recipe can be doubled, tripled, etc. and served cold or heated in the microwave for about 45 seconds before eating to enjoy warm.
* Variation: Use only 1/3 cup milk and stir in 1/3 cup nonfat plain Greek yogurt in the morning before serving.