01 - In a medium bowl or jar, combine oats, milk, Greek yogurt, cocoa powder, chia seeds (if using), maple syrup or honey, peanut butter, and vanilla extract.
02 - Stir thoroughly until well mixed and peanut butter is evenly incorporated throughout the mixture.
03 - Cover and refrigerate overnight, or for at least 6-8 hours, to allow oats and chia seeds to soften and thicken completely.
04 - In the morning, stir again. If the mixture is too thick, add a splash of milk to reach your desired consistency.
05 - Top with chocolate chips, chopped peanuts, and fresh fruit if desired. Serve chilled.