Preheat oven to 375 degrees. Trim all visible fat and tendons from chicken pieces, then cut each chicken breast lengthwise into 2 - 3 pieces. (I cut the larger ones into 3 and smaller ones in 2)
Spray a 9x13 baking dish with non-stick spray, then spread 1/2 cup basil pesto over the bottom of the dish
Lay chicken strips over the pesto, then spread 1/2 cup (or more) over the chicken. ( I use a rubber scraper to put the pesto in the dish and over the chicken) Sprinkle with Mozzarella cheese.
Cover the baking dish with aluminum foil and bake for 25-30 minutes, just until chicken is barely firm and cooked through. (Don't cook too much at this point, or the chicken will be overcooked by the time the cheese is melted and brown)
When chicken is barely cooked through, remove foil and sprinkle more cheese , if wanted, on top.
Put dish back into the oven without foil and cook 5 minutes more, just until cheese is melted.
After melting the cheese for 5 minutes I switch oven to broil and broil 5 minutes more, just long enough to get the cheese lightly browned.
Serve hot. There will be some flavorvul juice in the bottom of the dish when this is done, so you may want to serve with rice, Cauliflower rice, or quinoa to use the juice.