Preheat oven to 450 degrees F

Melt 1 tbsp. butter and olive oil in a deep nonstick frying pan or medium-high heat. Sprinkle the chicken with salt and pepper

Add the chicken to the pan and cook until golden and cooked through. Transfer to a plate to cool slightly then coarsely shred into bite size pieces. Place in a large bowl.

Add 1 tbsp. butter and oil back to the pan and add mushrooms. Saute over medium-high heat until the liquid evaporates from the mushrooms and they become pale golden. Add the onion, garlic, and thyme. Saute until the onion is translucent.

Add the wine and simmer until it evaporates. Transfer the mushroom mixture to the bowl with the chicken.

Melt 3 tbsp butter in the same pan over medium-low heat. Add the flour and whisk for 2 minutes. Whisk in the milk, cream, broth, nutmeg, 2 tsp salt, 3/4 tsp. pepper. Increase the heat to high. Simmer until the sauce thickens, whisking often, about 10 minutes. Add 1 tbsp. white truffle oil

Bring a large pot of salted water to a boil, add the penne regate and cook until al dente. Drain

Add the penne, sauce, peas, and parsley to the chicken mixture. Toss until the sauce coats the pasta and the mixture is well blended.

Butter a 13 x 9 x 2 inch baking dish and transfer the pasta mixture into the dish.

Mix the cheese and breadcrumbs in a small bowl and sprinkle over the pasta. Dot the remaining 3 tbsp. of butter on top.

Bake uncovered until golden brown and the sauce bubbles, about 25 minutes.