1. Preheat the oven to 350°F 175°C and lightly grease a 9×13 inch baking dish.

2. In a large skillet over medium heat warm the olive oil and sauté the diced onion until softened and fragrant about 3 to 4 minutes.

3. Add the ground beef to the skillet and cook breaking it apart with a spoon until fully browned. Drain off any excess grease.

4. Sprinkle the taco seasoning over the beef and pour in the water. Stir well to coat the meat and let it simmer for 2 to 3 minutes until slightly thickened.

5. Stir in the diced tomatoes with green chilies black beans and corn. Cook for another 2 to 3 minutes until heated through then remove from the heat.

6. In a medium bowl whisk together the sour cream cream cheese salsa salt and black pepper until smooth and creamy.

7. Spread about half of the crushed Doritos evenly over the bottom of the prepared baking dish.

8. Spoon half of the beef mixture over the Doritos and spread it into an even layer.

9. Sprinkle half of the cheddar cheese and half of the Monterey Jack cheese over the beef layer.

10. Drop spoonfuls of half of the creamy sour cream mixture over the cheese.

11. Repeat the layers with the remaining crushed Doritos beef mixture creamy layer and cheeses finishing with a generous layer of cheese on top. Reserve a small handful of crushed Doritos for garnish.

12. Sprinkle the reserved crushed Doritos over the top of the casserole.

13. Bake uncovered for 20 to 25 minutes or until the cheese is melted the edges are bubbling and the top is lightly toasted.

14. Remove from the oven and let the casserole rest for 5 to 10 minutes to set.

15. Top with shredded lettuce diced tomato onion cilantro and dollops of sour cream.

16. Scoop into bowls or cut into squares and serve warm.