If your chicken breasts are very thick, or are uneven, place them between layers if waxed paper and pound them down a little bit to an even thickness so they will cook at the same rate. If you don't have a meat pounder use a rolling pin or even a cast iron skillet.

Season the chicken on both sides with salt and pepper. Heat the butter and oil in a large skillet until sizzling, and then brown the chicken, cooking for a few minutes on each side. Do this in batches so as not to crowd the pan. Have the heat high enough that you get some color on the chicken, but not so high that it burns. Set aside.

Add the sauce to the pan and bring to a simmer. Nestle the chicken breasts back into the pan, cover (or use foil) and simmer gently for about 10 minutes, just until the chicken is cooked through. (You can check with an instant read thermometer ~ it should read 165F) Don't over cook your chicken, they don't need a lot of time.

Remove from heat and scatter about a cup of the mozzarella over the skillet. Arrange the rest of the toppings over the top. Finish with a little more mozzarella.

Put under the boiler (on the second shelf down, not right up against the flame) and broil until the cheese is melted and everything is bubbling. I like to let it get a little charred, so if your cheese isn't getting bubbly and browned, move the pan closer to the flame.

Finish with a dusting of Parmesan cheese and serve asap.

Note: this reheats fairly well in the microwave.