Spray a 12-inch by 8-inch by 1 1/2-inch baking dish with cooking oil spray. Place 12 chicken breast tenderloins in a layer on the bottom. Sprinkle the tenderloins evenly with 6 oz. Swiss cheese. In a small bowl, combine 1/4 cup milk and a 10 3/4-oz. can cream of chicken soup. Spread over top of chicken and cheese. Evenly sprinkle 2 cups of herb-seasoned stuffing mix over chicken soup layer. Drizzle 1/4 cup melted butter over top. Cover casserole with aluminum foil, and refrigerate for about 4 hours. Bake at 350 degrees for 55 minutes, or until casserole is nice and bubbly. Uncover casserole, and bake 5 to 10 minutes longer, until top is crisp and beginning to brown. The flavors mingle in this casserole to give an unbelievable taste--and the casserole is so simple to make! You may make this casserole ahead and refrigerate it up to 24 hours before baking, or you can even freeze it for a long peiod of time, then thaw it out and bake it! It is very versatile! I hope you like it!