CHICKEN TETRAZZINI

chicken bones from 3 cooked chickens, broken into 2- to 3-inch pieces
10 cups low-sodium chicken broth (from bouillon cubes)
4 carrots, thinly sliced
4 medium onions, coarsely chopped
6 celery ribs, cut into 1-inch pieces
1 head garlic, cloves smashed
2 tablespoons whole black peppercorns
4 California bay leaves
8 whole cloves
2 sticks unsalted butter
3 lbs mushrooms, thinly sliced
2 teaspoons salt
black pepper
8 tablespoons all-purpose flour
4 cups fat free evaporated milk
1/2 cup medium-dry Sherry (optional)

4 lbs spaghetti
chicken meat from 3 cooked chickens, torn into 1-inch pieces
4 cups freshly grated Parmigiano-Reggiano (please? we can get huge chunks at 
Sam's)

Bring chicken bones, broth, carrot, onion, celery, garlic, peppercorns, bay 
leaf, and cloves to a boil in a heavy saucepan, then simmer, partially 
covered, skimming froth, 30 minutes.

Pour stock through a large sieve into a bowl, discarding solids, and return 
to saucepan. Measure stock: If more than 8 cups, boil until reduced. Keep 
warm, covered.

Put oven rack in middle position and preheat oven to 350°F. Butter a shallow 
3-quart* glass or ceramic baking dish. *(ha ha!)

Heat half the butter in a large heavy skillet over moderately high heat 
until foam subsides, then sauté mushrooms with 1 teaspoon salt and 1 
teaspoon pepper, stirring, until liquid mushrooms give off is evaporated and 
mushrooms begin to turn golden, about 8 minutes.

Melt remaining butter in a heavy saucepan over low heat, then add flour and 
cook roux, whisking, 3 minutes. Add warm stock in a fast stream, whisking 
constantly, and bring to a boil. Reduce heat and simmer, whisking 
occasionally, 5 minutes. Add cream, Sherry(if using), remaining 1 teaspoon 
salt, and pepper to taste and simmer over low heat, whisking occasionally, 
10 minutes.

Cook spaghetti in a large pot of boiling salted water until al dente, then 
drain well.

Toss together spaghetti, mushrooms, and half of sauce in a large bowl, then 
transfer to baking dish. Stir together chicken meat and remaining sauce in 
same large bowl. Make a depression in spaghetti, then spoon chicken into it 
and sprinkle dish with cheese.

Bake until sauce is bubbling and top is lightly browned, about 30 minutes. 
Serve immediately.