Whisk the pesto sauce ingredients together in a large bowl. Add chicken and stir to evenly coat. Let chicken rest while you prep green beans (instructions to follow) and tomatoes (preferably 20-30 minutes) or cover and refrigerate up to 8 hours.
Transfer beans to a 9x13 baking dish and toss with 1 tablespoon olive oil, 1 tablespoon pesto, 1/4 teaspoon salt and 1/8 teaspoon pepper. Line green beans down the center of the pan, leaving room on both sides to add the tomatoes later.
While tomatoes are still on the cutting board, toss with 1 tablespoon olive oil, 1/8 teaspoon salt and 1/8 teaspoon pepper. Reserve for later.
Line chicken on top of green beans and spoon over any remaining pesto sauce from the bowl.
Cover pan with foil and bake at 400 degrees for 15 minutes. Uncover and line tomatoes on each side of chicken. Cover and bake an additional 15-30 minutes or until chicken is almost cooked through (an instant read thermometer should register 160 degrees F, and will reach 165 after chicken bakes with cheese. Cooking time may be more or less depending on thickness of chicken).
Top chicken evenly with mozzarella cheese and bake, uncovered, for 3 minutes or until melted.
Let chicken rest 5-10 minutes before slicing chicken. Serve Pesto Chicken with pasta, rice, couscous, etc.