12 ounces thin spaghetti
4 cups or so of diced cooked turkey
2 cups chicken or turkey stock, heated (canned is fine)
1 cup heavy cream
One-quarter cup dry sherry
Dash of cayenne pepper
1 pound fresh mushrooms, sliced
1 large onion, peeled, cut in half lengthwise, then sliced into thin half rounds
One stick (8 tablespoons) butter, divided
3 tablespoons all-purpose flour
1 cup dried bread crumbs
One-half cup grated Parmesan cheese
Salt and freshly ground pepper
Optional: 2 cups frozen peas, rinsed under cold water and drained, or one head of cooked broccoli florettes
Preheat the oven to 350 degrees F. Grease a large baking dish and set aside. Bring a large pot of salted water to a boil and cook the spaghetti for about two minutes less than the package recommends. It should be mostly tender but a little firm in the center. Drain and set aside. Melt 2 tablespoons of butter and combine with the bread crumbs and Parmesan cheese in a small bowl, and set aside.
While the spaghetti is cooking, melt 3 tablespoons of butter in a skillet large enough to hold all the ingredients (including the cooked spaghetti). Saute the onion with a little salt and pepper until it is just starting to brown, and add the mushrooms and cook for about 5 minutes more. Add the turkey to the skillet and turn off the heat.
At the same time, melt 3 tablespoons of butter in a large saucepan. Add the flour, cayenne, and a teaspoon of salt, and whisk to combine. Cook the mixture over medium heat for a couple of minutes, whisking constantly. Stir in the hot stock in 3 additions, whisking well to combine. When the mixture has thickened, turn off the heat and stir in the cream and sherry.
Put the spaghetti in the skillet with the turkey mixture, then pour the sauce over and mix everything well. Add the vegetables if you’re using them. Taste the mixture for salt and pepper. Pour into the greased baking dish, top with the crumb mixture, and bake for 30 minutes. Serve hot.