In a large skillet over medium-high heat, brown the ground beef along with diced onion, green bell pepper, and minced garlic for about 7-10 minutes until the meat is thoroughly browned and the vegetables are tender.

Once the meat is cooked, drain any excess fat, and stir in red salsa, salsa verde, taco seasoning, and chicken stock. Bring to a simmer over medium heat for about 4-5 minutes.

In a large bowl, combine the thickened meat mixture with sour cream, black beans, and cream of mushroom soup. Fold in half of the shredded Mexican cheese until well mixed.

Preheat your oven to 350°F (175°C). Grease a casserole dish. Layer 2 cups of crushed Doritos, then half of the meat mixture, and repeat, finishing with Doritos and remaining cheese.

Cover the casserole dish tightly with aluminum foil and bake for 30 minutes. Remove foil and bake for an additional 10-15 minutes until cheese is bubbly and golden.

Let the casserole cool for about 10 minutes before serving. Optionally top with diced tomatoes, shredded lettuce, chopped cilantro, olives, or a dollop of sour cream.