Preheat oven to 350 degrees.
If your chicken breasts are really fat, you might want to butterfly them or at least, flatten with a mallet. The larger, fatter the chicken breast, the longer they will take to cook.
Take a large skillet and put it over medium high heat. Mix all of your seasonings in a small bowl. Sprinkle one side of your chicken with half of the seasoning.
Add 1 1/2 T of olive oil to your warm skillet and add the seasoned side chicken to the pan. Sprinkle the top of the chicken breasts with the other half of the chicken.
Brown chicken for 4 minutes on each side. Place seared chicken in a baking dish.
Add the other 1 1/2 T of olive oil to the skillet and add the sliced mushrooms and sliced onion. Cook for about 4 minutes, until soft but not necessarily cooked through.
Pour on top of the chicken breasts. Add 2 T broth to skillet to scrape any browned bits left behind from the chicken or the onion and mushrooms. Pour this over the chicken.
Sprinkle mozzarella and parsley on top.
Bake for 35 minutes or until chicken is cooked through.