Heat a large skillet over medium heat. Add 1 pound lean ground beef and 1/2 diced onion. Cook, breaking the beef apart with a spatula, until the beef is no longer pink, about 4–6 minutes. Drain any excess fat and return the skillet to the heat.

Add 1 tablespoon taco seasoning, 1 can black beans (drained and rinsed), and 1 can green chiles to the cooked beef and onion. Stir to combine, then remove the skillet from the heat and set the filling aside.

Measure out the 1/2 cup vegetable oil and keep it nearby. Wipe or use a second large skillet for frying. Heat the frying skillet over medium-high heat and add about 2 tablespoons of the oil; heat until the oil shimmers but is not smoking.

Lay one small tortilla flat in the hot oil. Spoon about 3 tablespoons of the beef/bean/chile mixture onto one half of the tortilla and top with some of the 2 cups cheddar cheese.

Using a spatula or tongs, fold the tortilla in half over the filling (taco-style) and press gently to help it hold together.

Cook the folded taco 1–3 minutes on the first side, until golden brown and crisp, then carefully flip and cook the other side 1–3 minutes, until both sides are golden and crispy.

Transfer the cooked taco to a paper-towel-lined plate to drain. Add more oil to the skillet from the measured 1/2 cup as needed between batches to maintain a thin layer for frying.

Repeat steps 4–7 until all 24 small tortillas are filled and cooked. Work in batches sized to your skillet (for many skillets this is about 3–5 tacos at a time).

Serve the tacos hot. If desired, offer additional toppings at the table for people to pull apart and add to their tacos.