Cook rice according to package instructions using chicken broth instead of water. (Most long grain rice will use 1 1/2 cups of broth, but check your rice's package instructions in case you need more or less)
While rice is cooking, melt 2 tbsp butter in a large saucepan over medium high heat.
Add your mushrooms to the pan ensuring that they fully cover the bottom of the pan with little overlap. Do not stir for 3 minutes to allow mushrooms to brown.
Stir mushrooms and add onion and olive oil to the pan. Cook for another three minutes.
Add chicken, garlic, 1/2 tsp garlic salt, 1/2 tsp pepper, and 1/2 tbsp Italian seasoning, stirring well to combine with mushrooms and onions. Cook until chicken is browned, approximately 5 minutes.
Add flour and stir to coat all ingredients. Let the roux cook for 1-2 minutes without stirring.
Add the marsala wine, scraping the bottom of the pan for any browned bits and stirring occasionally until the sauce becomes thick, approximately 2-3 minutes.
Add the cream and reduce heat to medium low, simmering and stirring frequently to avoid burning the cream for 5 minutes.
Add 1/2 of the parsley, 1/2 of the parmesan, and the remaining salt, pepper, Italian seasoning. Stir the sauce well to evenly distribute all of the cheese and seasonings.
Fluff rice and mix in remaining butter.
Serve chicken and mushroom mixture on top of the rice, garnishing with remaining parsley and parmesan.