Prepare the stewed rhubarb: In a small saucepan, combine the chopped rhubarb, 2 tablespoons of maple syrup, and water. Bring to a simmer over medium heat. Cook for 8-10 minutes, stirring occasionally, until the rhubarb is tender and has broken down slightly into a chunky sauce. Remove from heat and let cool completely.

In a medium bowl or two individual jars, combine the rolled oats, milk, Greek yogurt, chia seeds, vanilla extract, and remaining 1 teaspoon of maple syrup (if using).

Stir the mixture thoroughly until all ingredients are well incorporated and the chia seeds are evenly distributed.

To assemble layers (optional, otherwise stir together): Divide half of the oat mixture into two jars/containers. Top with half of the cooled rhubarb sauce. Add the remaining oat mixture and top with the rest of the rhubarb sauce.

Cover the containers tightly with lids and refrigerate for a minimum of 4 hours, or preferably overnight, to allow the oats to soften and the mixture to thicken.

In the morning, stir the oats gently. If the mixture is too thick, add a splash of milk until the desired consistency is reached. Serve chilled, optionally topped with granola or a sprinkle of chopped nuts.