Garlic Herb Butter Filet Mignon with Crispy Rosemary Potatoes Step-by-step instructions

Before you start

Before you start, remove the steaks from the refrigerator and let them sit at room temperature for 20-30 minutes. This helps them cook more evenly. Pat the steaks dry with paper towels to ensure a good sear.

Wash and dry the potatoes. Set out all your ingredients and equipment: a cast-iron skillet, air fryer, chopsticks, sharp knife, tongs, and a large spoon. Have your instant-read thermometer ready.

Instructions

Crisp the Potatoes

1. 1Prepare the Potatoes
   Place a pair of chopsticks on either side of a baby potato. Using a sharp knife, slice the potato crosswise into thin accordion slits, stopping when the knife hits the chopsticks so the slices stay attached at the bottom. Repeat with all potatoes. In a bowl, toss the sliced potatoes with 1/2 tbsp olive oil, 1 sprig of rosemary (leaves removed and chopped), and 1/2 tsp flaky sea salt.
   Look for The potatoes have thin, even slits and are well coated with oil and salt.
   Tip Keep the slices about 1/8-inch apart for maximum crispiness.
2. 2Air-Fry the Potatoes
   Preheat the air fryer to 400°F (200°C). Arrange the sliced potatoes in the air fryer basket in a single layer. Cook for 20 minutes, shaking the basket halfway through, until the potatoes are golden and crispy on the outside and tender inside.
   Look for The potatoes are deeply golden and crisp, with the accordion slices fanned open.
   Tip Do not overcrowd the basket; cook in batches if needed.

The potatoes are sliced into thin, even accordion slits and coated with rosemary oil. As they air-fry, they will begin to puff and turn golden. The kitchen will smell of rosemary and toasted potato. After 20 minutes, they should be deeply crisp and slightly fanned open. Shake the basket halfway to ensure even browning.

Sear and Baste the Steaks

3. 3Season the Steaks
   Pat the filet mignon steaks dry with paper towels. Season generously on all sides with the remaining 1/2 tsp flaky sea salt and the freshly cracked black pepper.
   Look for The steaks are evenly coated with salt and pepper.
   Tip Seasoning just before searing helps form a great crust.
4. 4Sear the Steaks
   Heat a cast-iron skillet over high heat until smoking hot. Add the remaining 1/2 tbsp olive oil. Carefully place the steaks in the skillet and press down gently. Sear for 3 minutes without moving, until a deep mahogany crust forms.
   Look for The underside is deeply browned and releases easily from the pan.
   Tip Use tongs to press the steaks for even contact with the pan.
5. 5Flip and Add Butter
   Flip the steaks. Add the unsalted butter, smashed garlic cloves, the remaining rosemary sprig, and the thyme sprigs to the skillet. Tilt the pan slightly so the butter pools, and use a large spoon to continuously baste the steaks with the foaming butter.
   Look for The butter is foaming and fragrant with garlic and herbs.
   Tip Keep basting for about 2-3 minutes, tilting the pan to keep the butter from burning.
6. 6Cook to Temperature
   Continue basting until the internal temperature of the steaks reaches 130°F (54°C) for medium-rare, about 2-3 minutes more. For medium, cook to 140°F (60°C). Remove the steaks from the skillet and let them rest for at least 5 minutes.
   Look for The thermometer reads 130°F (54°C) in the center of the steak.
   Safe temperature 145°F (63°C) internal temperature (steaks, chops and roasts)
   Tip The temperature will rise about 5°F during resting.

The steaks are seasoned and seared in a smoking-hot skillet until a dark crust forms. Once flipped, the butter melts and foams as you add garlic and herbs.

The aroma is intensely savory and herbaceous. The steaks are basted continuously until they reach 130°F (54°C). The pan is sizzling and the butter is turning golden brown.

Rest and Serve

7. 7Rest and Carve
   Transfer the steaks to a cutting board and let them rest for at least 5 minutes. This allows the juices to redistribute. After resting, carve the steaks into thick slices against the grain.
   Look for The steaks are rested and juicy, and slicing reveals a rosy pink center.
   Tip Resting is essential for tender, juicy meat.
8. 8Serve with Pan Butter
   Arrange the sliced steak on plates alongside the crispy rosemary potatoes. Spoon the aromatic pan butter over the steak slices. Serve immediately.
   Look for The steak is glistening with herb butter and the potatoes are crisp.
   Tip Use all the pan butter—it is the sauce.

After resting, the steaks are carved into thick slices revealing a rosy pink center. The potatoes are crisp and golden. The pan butter is spooned over the top, adding a glossy sheen and rich flavor. The plate looks like it came from a fine steakhouse, and the first bite is tender, juicy, and packed with garlic herb goodness.

Common mistakes

One common mistake is not heating the skillet enough before adding the steaks. The pan should be smoking hot to get a good sear. Another is moving the steaks too soon—let them sear undisturbed for the full 3 minutes.

Overcrowding the air fryer can cause the potatoes to steam instead of crisp, so cook them in a single layer. Finally, do not skip the rest time; cutting into the steak too soon will release the juices.

How to tell it’s done

The steak is done when it reaches your desired internal temperature. For medium-rare, cook to 130°F (54°C) and let it rest to 135°F (57°C). For medium, cook to 140°F (60°C) and rest to 145°F (63°C).

Use an instant-read thermometer inserted into the thickest part of the steak. The potatoes are done when they are golden brown and crisp on the outside and easily pierced with a fork.

• Steaks, chops and roasts: 145°F (63°C) in the thickest part, then a 3-minute rest