Preheat oven to 350°F (175°C). Butter a 9x13 inch casserole dish.

Cook the pasta in a large pot of salted boiling water until al dente (slightly undercooked). Drain and set aside.

In a large skillet or Dutch oven, melt 1 tbsp butter over medium-high heat. Add mushrooms and sauté for 3-5 minutes until golden. Add onions and cook until soft. Add garlic and cook for 1 minute. Remove veggies from the pan and set aside.

In the same pan, melt the remaining 3 tbsp butter. Whisk in the flour and cook for 1-2 minutes until bubbly.

Slowly whisk in the chicken broth and lemon juice. Whisk until smooth. Stir in the half-and-half. Simmer for 5 minutes until thickened.

Return the chicken, mushroom mixture, and parsley to the sauce. Stir in the cooked pasta. Toss until everything is evenly coated.

Pour the mixture into the prepared baking dish. Top evenly with shredded mozzarella and parmesan cheese.

Bake for 20-25 minutes until the cheese is melted and bubbling. Broil for 2 minutes if a browner top is desired. Garnish with more parsley.