Garlic Herb Butter Filet Mignon with Crispy Rosemary Potatoes

This garlic herb butter filet mignon is seared to medium-rare perfection and paired with shatteringly crisp accordion Hasselback potatoes. The steak develops a deep mahogany crust, then gets bathed in foaming butter infused with garlic, rosemary, and thyme.

The potatoes are sliced into thin accordion slits, tossed with rosemary and olive oil, and air-fried until golden and crunchy. A truly steakhouse-worthy dinner that comes together in under an hour.

This recipe brings the steakhouse experience home with minimal fuss. Two thick filet mignon steaks are seasoned simply, then seared in a screaming-hot cast-iron skillet. The real magic happens when butter, smashed garlic, and fresh herbs hit the pan—basting the steaks continuously creates a rich, nutty, herbaceous sauce that clings to every slice.

On the side, baby golden potatoes are cut into accordion-style slits, tossed with olive oil and rosemary, and air-fried until they are impossibly crisp. The result is a restaurant-quality dinner that is surprisingly simple to execute.

Ingredients

Why this recipe works

The high-heat sear in a cast-iron skillet creates a deep, flavorful crust through the Maillard reaction, while the interior stays tender and juicy.

Basting with butter adds richness and helps transfer heat evenly, cooking the steak gently and infusing it with garlic and herb flavor. Letting the steak rest after cooking allows the juices to redistribute, ensuring every bite is moist and tender.

The accordion cut on the potatoes increases their surface area dramatically, which means more crispy edges and a fluffy interior. Air-frying circulates hot air around the potatoes, cooking them evenly and creating that shatteringly crisp texture without deep-frying. The rosemary and olive oil coating adds aromatic flavor that complements the buttery steak perfectly.

Notes and substitutions

For the best results, choose filet mignon steaks that are at least 1 1/2 inches thick. The thicker the steak, the easier it is to get a good sear without overcooking the center.

Flaky sea salt, such as Maldon, provides a nice crunch and dissolves evenly. If using regular table salt, reduce the amount by half. Fresh rosemary and thyme are essential for the butter baste; dried herbs will not infuse the same flavor.

A cast-iron skillet is ideal for searing because it retains heat well and can withstand high temperatures. If you do not have one, use a heavy stainless-steel pan. An instant-read thermometer is crucial for achieving the perfect doneness. For the potatoes, baby golden potatoes are preferred for their waxy texture and buttery flavor. You can also use small Yukon Gold or red potatoes.

• Baby golden potatoes: Small Yukon Gold or red potatoes, cut to similar size
• Fresh rosemary and thyme: 1 tsp dried rosemary and 1/2 tsp dried thyme, added with the butter
• Flaky sea salt: Kosher salt, using about 3/4 tsp
• Filet mignon: Ribeye or strip steak, adjusting cook time as needed

Equipment

• Cast-iron skillet
• Air fryer
• Chopsticks
• Sharp knife
• Tongs
• Large spoon
• Cutting board
• Instant-read thermometer