In a pin-size mason jar, stir together 1/2 cup milk and 1 tablespoon Nutella until combined. Stir in 1/2 cup of rolled oats and fix the lid onto the jar. Repeat with the other jar.
Place the jars into your refrigerator and let sit overnight (at least 8 hours).
Take the lid off one of the jars and top the oats with 1 tablespoon of Nutella and 1/4 cup of granola for serving.