Chicken Tetrazzini

Ingredients

• 0.3 teaspoon pepper black
• 5  peppercorns whole black
• 2 tablespoons butter 
• 1  carrots thinly sliced
• 2 rib celery stalks cut into 1-inch pieces
• 1 pound roasted chicken cooked (from 2 chickens)
• 2 pounds roasted chicken cooked (from 2 chickens)
• 3 tablespoons sherry 
• 2 tablespoons flour all-purpose
• 2  garlic clove smashed
• 1 cup cup heavy whipping cream 
• 4 cups chicken broth low-sodium
• 0.8 pound mushrooms thinly sliced
• 1 medium onion coarsely chopped
• 0.5 cup parmesan freshly grated
• 0.5 teaspoon salt 
• 0.5 lb pasta like spaghetti 
• 1  bay leaves 
• 6 tablespoons butter unsalted

Equipment

• bowl
• frying pan
• sauce pan
• oven
• whisk
• pot
• sieve
• baking pan
• wax paper

Directions

1. Bring chicken bones, broth, carrot, onion, celery, garlic, peppercorns, bay leaf, and cloves to a boil in a 3- to 4-quart heavy saucepan, then simmer, partially covered, skimming froth, 30 minutes.
2. Pour stock through a large sieve into a bowl, discarding solids, and return to saucepan. Measure stock: If more than 2 cups, boil until reduced. Keep warm, covered.
3. Put oven rack in middle position and preheat oven to 350F. Butter a shallow 3-quart glass or ceramic baking dish.
4. Heat 3 tablespoons butter in a large heavy skillet over moderately high heat until foam subsides, then saut mushrooms with 1/4 teaspoon salt and 1/8 teaspoon pepper, stirring, until liquid mushrooms give off is evaporated and mushrooms begin to turn golden, about 8 minutes.
5. Melt remaining 3 tablespoons butter in a 2- to 3-quart heavy saucepan over low heat, then add flour and cook roux, whisking, 3 minutes.
6. Add warm stock in a fast stream, whisking constantly, and bring to a boil. Reduce heat and simmer, whisking occasionally, 5 minutes.
7. Add cream, Sherry, remaining 1/4 teaspoon salt, and remaining 1/8 teaspoon pepper and simmer over low heat, whisking occasionally, 10 minutes. Stir in truffle butter (if using).
8. Cook spaghetti in a large pot of >boiling salted water until al dente, then drain well.
9. 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.
10. Bake until sauce is bubbling and top is lightly browned, about 30 minutes.
11. Serve immediately.
12. *Available at some specialty foods shops and D'Artagnan (800-327-8246).
13. Cooks' notes:Mushrooms can be sauted 1 day ahead and chilled, covered. Bring to room temperature before using. Sauce can be made 1 day ahead and cooled completely, uncovered, then chilled, its surface covered with wax paper.