Crockpot Chicken Tortilla Casserole

14 oz. tortilla chips, white or yellow, I've also used Doritos
5 chicken breasts, cooked and chopped
10 oz. diced tomatoes with chilies, drain slightly, I used Rotel
1 can cream of chicken soup
1 can cream of mushroom soup
1 c. chicken broth
2 cloves garlic, minced
1 onion, chopped
2 c. shredded cheese, I used Mexican
sour cream, optional

Line crockpot. Spread layer of chips on bottom, ok to overlap. In a large bowl, combine all other ingredients except cheese. Place half the chicken mixture on top of chips. Place half of cheese on top of chicken mixture. Repeat layers: chips, chicken mixture, cheese. Place lid on top and cook on low for 6 hours, or on high for 4 hours. Serve with additional chips if desired. Top with sour cream, if desired.