In a medium airtight container or glass mason jar, add all the ingredients in the order you like: oats, chia seeds, lemon zest, lemon juice, coconut milk, coconut yogurt, vanilla extract, sweetener, and eventually blueberries if you like.
Stir well to combine, it should be runny not overly thick.
Close the lid of the container, and place it in the fridge overnight, or for at least 3 hours. I recommend stirring after 1 hour to prevent the seeds from sinking to the bottom of the container.
Stir all the topping ingredients together. Add 1-2 tablespoons of coconut milk or more yogurt if too thick to your liking. Spread on top of the overnight oats the day before or just before serving.
Serve with extra lemon zest, desiccated coconut, blueberries, and crumbled shortbread cookies.