1Heat oven to 350ºF. Spray 2-quart casserole with cooking spray. In medium bowl, mix salsa verde and sour cream.
2Break up taco shells into bite-size pieces. Place half of shells in casserole. Top with shredded chicken, followed by half of salsa mixture. Top with half of the cheese. Repeat with remaining shells, salsa mixture and cheese.
3Bake about 30 minutes or until cheese is melted and top is golden brown. Let stand 5 minutes before serving.