In a large mixing bowl, combine the rolled oats, almond milk, cocoa powder, maple syrup, vanilla extract, and salt. Stir until well combined.
If using, fold in the Greek yogurt for added creaminess.
Stir in the chocolate chips, reserving a few for topping if desired.
Divide the mixture evenly into two or four jars or containers with lids.
Seal the jars and refrigerate overnight (or at least 4 hours) to allow the oats to soak and soften.
In the morning, give the oats a good stir. Top with chopped nuts and fresh berries if desired before serving.