Preheat oven to 350°F (175°C).
In a large skillet over medium heat, cook ground beef, diced onion, and minced garlic until the beef is browned and the onion is soft, about 7-8 minutes. Drain excess fat.
Add taco seasoning mix and 1 cup water to the skillet. Stir well and simmer for 5 minutes until the mixture thickens slightly. Remove from heat.
In a medium bowl, combine sour cream, cream of chicken soup, and 1 cup of shredded cheddar cheese. Mix until smooth.
In a 9×13 inch casserole dish, spread half of the Doritos evenly on the bottom.
Layer the seasoned beef mixture evenly over the Doritos.
Spread the sour cream and soup mixture evenly over the beef layer.
Sprinkle the remaining 1 cup of shredded cheddar cheese over the top.
Top with the remaining Doritos, gently pressing them into the cheese layer.
Cover the casserole tightly with aluminum foil.
To freeze: Place the covered casserole in the freezer for up to 3 months.
To bake from frozen: Preheat oven to 350°F (175°C). Remove foil and bake casserole covered for 45 minutes, then uncover and bake an additional 10 minutes until cheese is bubbly and Doritos are slightly browned.
To bake from thawed: Thaw casserole in the refrigerator overnight. Preheat oven to 350°F (175°C). Bake covered for 30 minutes, then uncover and bake an additional 10 minutes until cheese is bubbly and Doritos are slightly browned.
Remove from oven and let stand for 5 minutes before serving.
Garnish with chopped fresh cilantro if desired.