In a medium-sized bowl or jar, mix together the milk, Greek yogurt, pumpkin puree, maple syrup, and vanilla extract. Stir until smooth and fully combined.
Add the chia seeds, oats and pumpkin spice to the mixture. Stir again, ensuring the oats are evenly coated.
Cover the bowl or jar and refrigerate for at least 4 hours, or preferably overnight, allowing the oats to soak and soften.
Before serving, prepare the magic shell. In a small microwave-safe bowl, combine the dark chocolate chips and refined coconut oil.
Microwave the chocolate-coconut oil mixture in 15-20 second intervals, stirring between each interval until the chocolate is completely melted and smooth. Drizzle it over the top of your overnight oats to form a thin layer.
Place the overnight oats in the fridge or freezer for a few minutes for the chocolate to harden and form a magic shell. Break it with a spoon, and enjoy your pumpkin spice overnight oats with a delicious, crunchy topping!