02Spread 1 tablespoon of butter over a 13 by 9 by 2-inch baking dish.
03Melt 1 tablespoon each of butter and oil in a deep large nonstick frying pan over medium-high heat.
04Sprinkle the chicken with 1/2 teaspoon each of salt and pepper.
05Add the chicken to the hot pan and cook until pale golden and just cooked through, about 4 minutes per side.
06Transfer the chicken to a plate to cool slightly.
07Coarsely shred the chicken into bite-size pieces and into a large bowl.
08Meanwhile, add 1 tablespoon each of butter and oil to the same pan.
09Add the mushrooms and saute over medium-high heat until the liquid from the mushrooms evaporates and the mushrooms become pale golden, about 12 minutes.
10Add the onion, garlic, and thyme, and saute until the onion is translucent, about 8 minutes.
11Add the wine and simmer until it evaporates, about 2 minutes.
12Transfer the mushroom mixture to the bowl with the chicken.
13Melt 3 more tablespoons butter in the same pan over medium-low heat.
14Add the flour and whisk for 2 minutes.
15Whisk in the milk, cream, broth, nutmeg, remaining 1 3/4 teaspoons salt, and remaining 3/4 teaspoon pepper.
16Increase the heat to high.
17Cover and bring to a boil.
18Simmer, uncovered, until the sauce thickens slightly, whisking often, about 10 minutes.
19Bring a large pot of salted water to a boil.
20Add the linguine and cook until it is tender but still firm to the bite, stirring occasionally, about 9 minutes. Drain.
21Add the linguine, sauce, peas, and parsley to the chicken mixture.
22Toss until the sauce coats the pasta and the mixture is well blended.
23Transfer the pasta mixture to the prepared baking dish.
24Stir the cheese and breadcrumbs in a small bowl to blend.
25Sprinkle the cheese mixture over the pasta. Dot with the remaining 3 tablespoons of butter.
26Bake, uncovered, until golden brown on top and the sauce bubbles, about 25 minutes.