Pre-heat the oven to 200 degrees Celsius (fan) and roast all the hazelnuts for 10 minutes, then roughly chop them.
In a bowl, mix the oats, cacao powder, almond milk, maple syrup and half of the hazelnuts. Spoon the almond butter into the bottom of a clean jar and then pour the cacao/oat mixture on top.
Store the jar in the fridge overnight (≤ 5°C) with an airtight lid on it.
In the morning sprinkle over the remaining hazelnuts, and enjoy!