Preheat oven to 400 degrees. Lightly spray a 9 x 13" baking dish with non-stick spray. Set prepared baking dish aside.
In a mixing bowl, combine the soup, milk, salt and pepper until combined. Add in the chicken and thawed peas and carrots. (Frozen peas and carrots can be microwaved for 2-3 minutes until no longer frozen.) Stir ingredients together until well coated in the soup mixture.
Pour the chicken and soup mixture into the prepared baking dish. Spread evenly with a rubber scraper into the bottom of the pan. Top the chicken mixture with 1 1/2 cups of the shredded cheese, reserving the remaining 1/2 cup for topping the casserole. On top of the cheese layer, add on the package of frozen tater tots into an even layer. (Tots don't need to be thawed.)
Bake the casserole for 28-30 minutes or until the tater tots are golden brown. Remove from oven and sprinkle on the remaining 1/2 cup of shredded cheese on top of the tater tots. Bake for another 5 minutes until the cheese is melted.
Remove from oven and let cool for 5-10 minutes before serving.
Notes
Storage: Store baked and cooled casserole in the pan covered with press-and-seal wrap refrigerated. Casserole can also be stored in individual containers refrigerated. Kept refrigerated, casserole will keep for up to 5 days.Freezing: Casserole can be prepped and frozen in aluminum freezer pans. Cover top with press-and-seal wrap and aluminum foil. Kept frozen, casserole will keep for up to three months. Thaw casserole completely before baking.