Air Fryer Steak Frites

Pat the steak dry using paper towels, and place it on a wire rack-lined baking sheet. Sprinkle both sides and the edges of the steak evenly with 1 ½ teaspoons of the salt. Refrigerate the steak, uncovered, for at least 8 hours or up to 48 hours.

Meanwhile, stir together the softened butter, chives, thyme, rosemary, Worcestershire sauce, garlic powder, and ¼ teaspoon of the salt in a small bowl. Cover and refrigerate until ready to use. (Alternatively, place the butter mixture on parchment paper or plastic wrap, and roll it into a log. Seal the edges, and refrigerate until ready to use.)

Remove the steak from the refrigerator 30 minutes before cooking. While the steak comes to room temperature, preheat the air fryer with 1 large, flat perforated basket to 400 degrees. Brush the steak evenly with 1 tablespoon of the oil. Place the steak in the basket of the air fryer; cook it, undisturbed, until it is golden brown on top and an instant-read thermometer registers 125 degrees for medium-rare or 135 degrees for medium, 10 to 12 minutes or until the desired degree of doneness (continue cooking and checking the temperature every 2 minutes). Remove the steak from the air fryer and place it on a cutting board. Sprinkle it with pepper, and let it rest while preparing the fries (do not cut into it). 

Place the frozen fries in a large, heatproof bowl. Pour any remaining juices and fat from the air fryer over the frozen fries. Add the remaining 2 tablespoons of oil to the frozen fries, and toss to evenly coat. 

Heat the air fryer to 400 degrees. Add the frozen fries to the air fryer basket, and shake to evenly distribute them. (Save the bowl for tossing the fries after cooking.) Place the basket in the air fryer and cook, shaking the basket every 4 to 5 minutes, until the fries are golden brown and crispy, 14 to 15 minutes. Remove and transfer the fries to the same large, heatproof bowl. Sprinkle them with the sea salt or truffle salt, and toss to fully coat.

Carve the rested steak from the bone, and cut it into ¾- to 1-inch slices. Place the steak on plates, and pile the fries alongside. Spoon or slice 1 ½ tablespoons of the compound butter over the sliced steak, and sprinkle it lightly with a pinch more kosher salt. Serve immediately.