Preheat oven to 350°F. Cover a baking sheet with foil or parchment paper.
Place hazelnuts on the prepared baking sheet and roast in the oven for 10-15 minutes. Let cool. Remove as much of the skins as you can by rolling the hazelnuts around using your hands.
Place the hazelnuts into a blender or food processor and blend them to as fine of a consistency as you can get them. Add the maple syrup and cocoa powder and blend to combine.
Gradually pour in the water. You may not need all of the water if you like a thicker consistency. Store in the fridge in a sealed container. Lasts up to 2 and a half weeks.