Coat the chicken on both sides with the flour mixture, shaking off any excess, then dip both sides into the egg mixture and dredge both sides in the bread crumbs mixture.
Heat the oil in a large sauté pan, ½ inch up to the skillet side, and cook breaded thighs on medium-high for 2 to 3 minutes on each side until the chicken is golden brown on each side. Do not overcrowd the skillet. Remove and place in a cookie sheet.
Smear tomato sauce over the chicken and top with a mozzarella slice.
Place in the oven and cook until the mozzarella has melted.