Melt the ghee in a cast iron skillet over medium heat, then toss in peeled and chopped shallots and minced sage, frying them until they release their fragrance and become translucent – about 3 minutes. Toss in diced yam, and fry until tender when pierced with a fork, stirring frequently.
Add the leftover turkey to the yams and shallots, and continue frying for 5. Deglaze the skillet with one cup roast chicken or turkey stock, and simmer the hash until the liquid is completely evaporated, about ten minutes longer. Serve warm.