Season chicken with salt and pepper. Sprinkle a small amount of cornstarch onto both sides of each chicken breast and rub in.
Melt butter in a large skillet. Add chicken and cook for 4-5 minutes. Flip and cook the other side until chicken is cooked through. Remove from skillet and transfer to a plate.
Add onion and garlic to the same skillet. Cook until onion becomes translucent, about 2 minutes. Add chicken broth, lemon juice and mushrooms. Cook until mushrooms become tender, about 3-4 minutes. Add a small pinch of thyme and stir to combine. Season with salt and pepper. Add a small amount of cornstarch if you want to thicken the sauce.
Add chicken back into the pan. Top each pieces with a small amount of Mozzarella cheese. Top with lid and cook just until cheese is melted, about 1 minute. Remove from skillet and serve with sauce. Enjoy!
by The Savvy Kitchen