This is a quick, easy dish that should be made as close to eating as possible. It can be prepped ahead of time, but only takes a few minutes to finalize. Substitute gluten-free flour to make this for guests with gluten sensitivities.
Slice the chicken breasts lengthwise and pound flat. You should be able to get 3 slices out of each breast. I usually cut the long breast pieces in half so you are working with pieces no more than 4 inches in length.
Mix flour, salt, and pepper on a plate. Dredge the breasts in the flour and pat them to remove excess flour.
Melt butter in a large skillet over medium heat, then place the chicken breasts in the pan and cook until it is lightly browned, about 3-4 minutes. Turn and cook on the other side until lightly browned.
Remove the chicken breasts from the pan, pour over the marsala and cook for two or three minutes until the sauce is slightly thickened. Return the chicken breasts to the pan, cover with a slice of mozzarella cheese and heat until the cheese starts to melt. You can place a lid over the pan to melt the cheese faster so the chicken doesn't overcook. Place the chicken breasts on a serving platter and spoon over the marsala sauce. Serve immediately.
Notes
You can easily substitute gluten-free flour to make this a gluten-free dish.