Place cashews in a medium bowl and add water to cover by 1”. Let soak at room temperature overnight.
Drain cashews well and transfer to a blender. Add 1 cup water, coconut milk, agave, and vanilla. Blend on high speed until very smooth. If using xanthan gum, with the blender running, add xanthan very gradually through the hole in the blender lid until fully incorporated.
Strain coconog through a fine mesh strainer into a punch bowl or pitcher. Stir in rum and orange liqueur. Cover and refrigerate for at least 1 hour to allow the flavors to meld.
If not using xanthan gum, the coconog may separate during refrigeration. Let sit at room temperature for 20 minutes, then whisk well to bring everything back together.
Serve in small glasses and grate fresh nutmeg over the top of each serving.