Sauté the Vegetables: In a large pot, heat the butter over medium heat. Add the minced garlic and chopped onion. Cook, stirring frequently, until the onion is softened and translucent, about 5 minutes.
Add Flour: Add in the flour, stir frequently and cook for 1 minute.
Build the Soup Base: Pour in the chicken broth and the half and half. Bring the mixture to a boil. Once boiling, reduce the heat to a simmer.
Add Beans, Corn, and Chicken: Stir in the cream of chicken soup, salsa, shredded chicken, beans, and corn.
Add the Seasonings: Stir in the cumin and fajita seasoning. Continue to simmer over medium-low heat for 15 minutes to allow the flavors to combine.
Serve and Garnish: Ladle the soup into bowls and top with grated Monterey Jack cheese and crushed tortilla chips. Add a dollop of sour cream and sliced avocado for extra creaminess, if desired.