In a mason jar or small bowl, combine the rolled oats, cocoa powder, and sea salt. Stir with a fork until the cocoa powder is evenly distributed through the oats with no clumps remaining.
Add the maple syrup, milk, Greek yogurt, and vanilla extract to the jar. Stir thoroughly until all ingredients are well combined and the mixture looks smooth and chocolatey.
Fold in the mini chocolate chips, reserving a few for topping if desired. Make sure they're evenly distributed throughout the mixture.
Cover the jar tightly with a lid or plastic wrap and refrigerate for at least 4 hours, or preferably overnight for 8-12 hours.
In the morning, give the oats a good stir. If they're too thick, add a splash of milk until you reach your desired consistency.
Top with additional chocolate chips, fresh berries, sliced banana, or a dollop of nut butter before serving. Enjoy cold straight from the refrigerator.
