Preheat oven to 375F.
Lightly grease a 9x13 baking dish with cooking spray and set aside.
In a large skillet over medium-high heat, melt 1/2 tablespoon butter and add 1/2 tablespoon olive oil.
Add sliced mushrooms and sliced onions to the skillet; season with salt and pepper, and cook for 5 minutes.
Stir in the garlic and cook for 30 more seconds, or until fragrant.
Transfer half of the mushrooms mixture to the prepared baking dish; set the rest aside for later.
Return skillet to heat and add the rest of the butter and olive oil.
Season the chicken breasts with salt, pepper, garlic powder, paprika, and Italian Seasoning.
Add chicken breasts to the hot oil - you may have to do this in batches if skillet isn't big enough - and cook chicken breasts for 2 minutes per side, or until lightly browned.
Remove chicken breasts from skillet and arrange over mushrooms in the baking dish.
Return skillet to the stove; add chicken broth and scrape up the browned bits. Bring mixture to a boil and cook for 4 to 5 minutes, or until liquid is reduced.
Top chicken breasts with the rest of the mushrooms mixture, add cheese over the chicken breasts, and pour in the prepared chicken broth.
Bake uncovered for 15 minutes, or until chicken is cooked through.
Remove from oven.
Garnish with fresh parsley.