Roast hazelnuts in a 350F/180C oven for 5 min. You don't want to actually roast them but dry the peel. When the nuts have cooled, place them in a dishtowel and roll around to rub off the peel. Pick out from the peel and place in a cup or jar with water till covered. Soak 8+ hrs.
Drain the hazelnuts, blend (in a blender, food processor, or immersion blender) with one cup water until hazelnuts or finely ground. Squeeze the milk through a nut milk bag or cheesecloth.
Sprinkle the gelatin on 1/4 cup cold water, let sit to bloom.
Heat the hazelnut milk with salt, ghee, and maple syrup until it starts to steam. Stir in the bloomed gelatin. When it cools to room temperature, I put it in the freezer to speed up the firming process. Every 10 min or so, mix with a mixer or immersion blender until the mixture has firmed up.