2 cups shredded, cooked chicken
1 1/2 cups shredded mozzarella or cheddar cheese, divided
1 can condensed cream of chicken soup (NOT diluted)
1/2 cup milk
1/2 cup sour cream
1 (10 ounce) can Ro-tel tomatoes, drained (or substitute with about 1.25 cups petite-diced tomatoes for a mild option)
1/2 of a 1-ounce packet (about 4 teaspoons) dry Ranch seasoning mix (just the dry seasoning)
1 (9.75 ounce) bag Doritos Cool Ranch chips, coarsely crushed (about 4 cups crushed)