Preheat the oven to 350°F (175°C) and lightly grease an 11×7-inch baking dish.
In a large skillet over medium-high heat, brown 1 1/2 pounds ground beef, breaking it up as it cooks; drain any excess fat.
Return the beef to the skillet and stir in 1 teaspoon seasoned salt, 1 package taco seasoning, the 14.5-oz can diced tomatoes with juice, 15-oz tomato sauce, and the 4-oz can chopped green chilies; reduce heat and simmer uncovered for 15–20 minutes.
While the sauce simmers, whisk together 2 lightly beaten eggs and 2 cups (16 oz) cottage cheese in a small bowl until combined.
Assemble the casserole in the prepared baking dish: layer half of the meat sauce, half of the torn 12 small corn tortillas, half of the cottage cheese–egg mixture, and half of the 3½–4 cups shredded Cheddar/Monterey Jack; repeat the layers once more finishing with the remaining shredded cheese on top.
Bake uncovered at 350°F for about 30 minutes, or until the casserole is bubbly and the cheese is melted.
Let the casserole stand 5 minutes, then top with 2–3 cups broken tortilla chips, diced tomatoes, avocado chunks, and salsa to taste; serve immediately.