Boil the chopped potatoes in lightly salted water for about 20 minutes, until soft. You can saute the minced garlic cloves, or bake them whole for a very mild flavor, or leave them raw if you really like a garlic kick. Drain the potatoes. You can save some of that water for the gravy if you like. Leave a small amount of water in to mash them with. Mash the potatoes with the garlic, milk, coconut oil and salt to taste. You can use a hand blender or beaters to make the potatoes extra creamy.
While the potatoes boil, saute the mushrooms in the oil until they are soft and dark, about 20 minutes. Once they have released and then reabsorbed their own liquid, deglaze the pan with red wine. Add the balsamic vinegar and water, along with a pinch of salt to bring the flavors together. Dissolve the arrowroot or kudzu (or flour) in a small amount of water. Stir it into your gravy until it is nearly boiling and it thickens. Serve the gravy over a large scoop of mashed potatoes.