Place the potatoes in a medium saucepan, cover with cold water and bring to a boil. Reduce the heat; simmer until just tender, about 7 minutes. Drain and set aside. Heat 3 tbsp of butter in a large non-stick skillet over medium heat. Add the apple and cook until golden, about 11 minutes. Transfer to a plate and set aside.
Add the remaining 2 tbsp of butter, onion and celery to skillet; cook until slightly softened, 9 to 10 minutes. Add the wine and cook until the liquid has almost evaporated. Add the turkey, potatoes, cream and stock, simmer until the sauce is creamy and the vegetables are tender, about 12 minutes. Stir in the sage and apple; season with salt and pepper. Spoon mix onto buttered toast and drizzle with sauce. (I added cranberry sauce to the toast and skipped placing the hash on the toast.)