Combine Ingredients: In a medium-sized mixing bowl, combine the rolled oats, milk, cooled espresso, sweetener, chia seeds (if using), vanilla extract (if using), and chocolate chips.

Mix Well: Stir the mixture thoroughly to ensure all ingredients are evenly distributed. This step is crucial to avoid clumps and ensure the flavors meld together.

Transfer to Containers: Divide the mixture evenly between two mason jars or airtight containers.

Refrigerate: Seal the jars or containers and place them in the refrigerator for at least 6 hours, preferably overnight, to allow the oats to absorb the liquid and soften.

Stir Before Serving: Before eating, give the oats a good stir to redistribute any settled ingredients and achieve a uniform texture.

Add Toppings: Top with fresh fruit, nuts, or granola as desired for added flavor and texture.