How to Make It
In a large saucepan, combine the turkey legs with the chicken stock and, if necessary, water to cover. Bring to a boil, then reduce the heat to moderately low and simmer until the meat is cooked through, about 1 hour. Using tongs, transfer the turkey to a cutting board and let cool. Simmer the stock over moderately high heat until reduced to 4 cups, about 20 to 40 minutes. Shred the meat and discard the skin and bones.
Preheat the oven to 425°. In a large pot, melt 4 tablespoons of the butter. Add the carrots, celery, onion, fennel, thyme and nutmeg and cook over moderately high heat, stirring occasionally, until lightly browned, about 5 minutes. Add the flour and cook, stirring, for 1 minute. Add the reduced stock, bring to a boil and cook, stirring occasionally, until the sauce is thickened, about 5 minutes. Add the turkey, cream, peas and parsley, season with kosher salt and pepper and cook over moderate heat, stirring occasionally, for 5 minutes. Spread in a 9-by-13-inch baking dish.
In a large skillet, melt the remaining 3 tablespoons of butter. Add the mushrooms and cook over moderately high heat, stirring occasionally, until browned, about 5 minutes. Add the leeks and cook, stirring occasionally, until softened, about 5 minutes. Stir in the tarragon. Spread the mushroom mixture over the turkey in the baking dish.
Spread the tots over the mushroom mixture. Bake for 45 minutes, until bubbling and golden. Sprinkle with sea salt and serve with hot sauce, if desired.