Preheat the oven to 375 degrees F. Lightly oil a 9-by-13-inch casserole dish.
Heat the oil in a large skillet over high heat. When the oil is shimmering, add the beef and sprinkle with the chili powder, cumin, oregano, 1 teaspoon salt and a few grinds of pepper. Cook, breaking up the meat into smaller pieces, until browned, about 5 minutes. Add the onions and garlic and cook until the onions are soft, about 5 minutes more. Add the beans, salsa and 1/2 cup water and bring to a simmer; cook until the sauce thickens and coats the meat, about 5 minutes. Add salt and pepper to taste. (This beef-and-bean mixture can be made up to a day ahead of time.)
Lay half the tortilla chips on the bottom of the oiled casserole dish. Spread half the meat mixture on top. Sprinkle half the cheese blend over the meat. Repeat with the remaining chips, meat and cheese. Bake uncovered until the cheese melts and the casserole is hot, about 20 minutes.
Top with sour cream, lettuce, tomato, avocado and pickled jalapenos if desired. Serve with more salsa and tortilla chips on the side.
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