In a jar, combine the oats, chia seeds, salt, cinnamon, and nutmeg. Add in the milk, yogurt, vanilla extract and vanilla bean seeds (if using). Divide the banana into thirds. Mash two thirds of it well with a fork and add to the jar with the oats. Slice the remaining third and add this to the jar as well. Place the lid on the jar and shake vigorously until the mixture is evenly combined (this may take a minute or two). Refrigerate overnight.
Remove the jar lid, sprinkle nuts and/or sugar over oatmeal as desired. Serve.