Preheat oven to 350°F.
Prepare a shallow baking dish (~ 3 quarts in size, or an equivalent)
Homemade Chicken Stock (optional)
Bring chicken bones, broth, carrot, onion, celery, garlic, peppercorns, bay leaf, and cloves to a boil in a 3- to 4-quart heavy saucepan
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 2 cups, boil until reduced.
Keep warm, covered
In a large skillet over medium-high heat, add the oil
Sprinkle the chicken with a pinch of sea salt and a grind of black pepper
Add the chicken and cook until pale golden and just cooked through (~ 4 minutes per side). Transfer the chicken to a plate to cool slightly.
Coarsely shred the chicken into bite-size pieces and into a large bowl
Mushrooms and Onions
In a large heavy skillet over medium-high heat, warm 3 Tbsp butter
Add the mushrooms, along with a pinch of sea salt and a grind of black pepper
Sauté until the liquid given off by the mushrooms has evaporated and they've begun to turn golden ( ~ 8 - 10 minutes)
Add the onion, garlic, and thyme, and saute until the onion is translucent (~ 5 - 8 minutes)
Add the wine and simmer until it has evaporated (~ 3 - 5 minutes)
Transfer the mushroom/onion mix to the bowl with the chicken
To the same pan over medium-low heat, melt the additional 3 Tbsp butter
Add the flour and whisk for 2-3 minutes
Whisk in stock, Greek yogurt, white wine, another pinch of sea salt and a grind of black pepper. Bring to a slow boil
Reduce the heat to low and simmer, uncovered, whisking often, until the sauce has thickened slightly (~ about 10 minutes)
Stir in truffle butter or oil, if using
Bring a large pot of salted water to a boil.
Add the linguine and cook according to the package directions, until it's al dente
Add the linguine, sauce, peas, and parsley to the chicken mix. Toss until the sauce coats the pasta and the mixture is well blended
Transfer to the prepared baking dish.
In a small bowl, combine the cheese and breadcrumbs. Sprinkle over the pasta.
Bake until sauce is bubbly and the top is lightly browned about 30 minutes