In a medium mixing bowl or a large mason jar, combine the rolled oats and almond milk. Stir well to ensure the oats are evenly coated.
Add the diced apple, maple syrup, ground cinnamon, vanilla extract, and a pinch of salt to the mixture. If you choose to use Greek yogurt, now is the time to add it for an extra creamy texture. Mix all the ingredients thoroughly until everything is well incorporated.
Before sealing, taste the mixture to see if you'd like to add more sweetness or additional cinnamon. Adjust according to your preference.
Cover the bowl with plastic wrap or seal the mason jar with the lid, then refrigerate overnight or for at least 4-6 hours. This allows the oats to absorb the liquid and flavors.
In the morning, take the oats out of the fridge and stir them well. If the oats appear too thick for your liking, mix in a splash more of almond milk to reach your desired consistency.
Before serving, sprinkle the top with the chopped walnuts or pecans for an enjoyable crunch.
Notes
Serve in clear glass bowls and garnish with apple slices and cinnamon for an attractive presentation.