In a small saucepan, heat up butter or coconut oil over medium heat. Add bananas, vanilla, and cinnamon to the heated pan and begin to sauté until they begin to break down and juice out its natural sugars – about 2-3 minutes.
Add maple syrup, stir to combine, and cook for another minute, remove from heat.
Place 1/4 cup of steel-cut oats, 1/2 teaspoon ground flax (optional), and 1/2 cup of milk inside each jar.
Spoon bananas foster mixture into all the jars, mix with a spoon to combine, cover, and refrigerate for 8 hours or overnight.
In the morning, eat cold, straight out of the jar, or warm up in the microwave if desired.