Bring chicken broth to a boil in a small saucepan. Add quinoa and bring to a boil. Cover and reduce heat to low and cook for about 15 minutes. Remove from heat and let sit for 5 minutes. Fluff with a fork and set aside.
In a medium saucepan, combine crushed tomatoes, tomato paste, pesto, and balsamic vinegar over medium heat and bring to a simmer.
Then add half and half, crushed red pepper flakes, and salt and pepper. Cook until heated through.
In a large bowl, mix together chicken, quinoa, Parmesan cheese, 1/2 cup mozzarella cheese, and sauce. Mix well.
Pour into a greased 9x13-inch baking dish and then top with remaining 1/2 cup mozzarella and sliced tomatoes.
Bake in a preheated 375 degree oven for 12 to 15 minutes or until cheese has melted and the casserole is heated through.