Combine the ingredients for the au jus in a saucepan. Warm the mixture over medium heat and whisk for 5 minutes until they combine. Remove the au jus from heat and set it aside.

Pat the skirt steak with a towel to remove excess moisture. Then, coat it with olive oil, kosher salt, and black pepper.

Preheat the air fryer to 400℉ (204℃). Add both or half of the skirt steak to the air fryer basket, depending on the size of your air fryer. Cook for 6-8 minutes, flipping the steak halfway through.

Remove the steaks and let them rest for 10 minutes. Slice the skirt steak against the grain and set it into the bowl with the reserved au jus.

Meanwhile, butter the bread and sprinkle them with garlic powder. Then, layer the meat onto the bread slices and top them with cheese.

Line the sandwiches into to the air fryer basket and cook at 350℉ (176℃) for 2-3 minutes or until the cheese melts. Serve the sandwiches with a side of au jus and horseradish cream sauce, and enjoy!