Place 3.5 ounces of hazelnuts in a large container, fill with water and leave to soak overnight. Drain the water, rinse, and place the hazelnuts and 2 cups of water in a blender. Blend until hazelnuts have completely broken down. Place muslin/cheese cloth over a colander and place in a large bowl. Pour the liquid over the cloth, then pull up on all ends to squeeze out as much liquid as possible. Serve straight away or store in the refrigerator until you are ready to use. It will keep fresh for 5 days. The milk might separate a bit while it sits, just give it a quick stir or shake and it’s ready.