Make seasoning: In a small bowl, combine chili powder, cumin, cornstarch, salt, paprika, black pepper, garlic powder, onion powder, oregano, and cayenne. Set aside.

Cook beef: In a large skillet over medium heat, cook ground beef until browned, breaking up into small crumbles. Drain any grease if needed. Add seasoning blend and stir to coat evenly. Add black beans if using, and keep mixture warm on low.

Fry taco shells: Heat 1 inch of oil in a skillet to 325°F (160°C). Using tongs, dip one half of a tortilla into the hot oil while holding the other half up to form a U‑shape. Fry each side about 1 minute until golden and crisp. Transfer to paper towels to drain. Repeat.

Assemble: Spoon beef mixture into taco shells. Top with lettuce, cheese, tomatoes, and sour cream. Add salsa, guacamole, or toppings of your choice. Serve immediately.