Dry-Brine the Steak

1. Pat the steak completely dry with paper towels, then season both sides with salt equal to about 1% of the steak’s weight. For a 16 oz (454 g) steak, that’s about 0.16 oz (4.5 g), or roughly:
   1 1/2 teaspoons Diamond Crystal kosher salt,
   1 teaspoon Morton kosher salt,
   or 3/4 teaspoon table salt.
2. Place the steak on a wire rack set over a baking sheet and refrigerate uncovered for at least 1 hour. For deeper flavor and a better crust, dry-brine for 2-4 hours.
3. If you don’t have at least an hour, skip the dry brine and salt the steak immediately before searing, or add salt to the sliced steak after cooking.

Prepare the Potatoes

1. Cut the potatoes into 1/4- to 1/3-inch (0.6- to 0.8-cm) fries, keeping them as even as possible. Place them in cold water as you cut to prevent browning.
2. Transfer the cut potatoes to a colander and rinse under cold running water for about 15 seconds to remove excess starch. Drain well, then pat completely dry with paper towels.

Blanch the Fries at 275°F (135°C)

1. Pour the oil into a deep fryer or heavy pot, following the fryer’s fill guidelines or filling the pot no more than one-third full. Heat to 275°F (135°C).
2. If using a pot, monitor the oil temperature with a thermometer. Without one, dip the end of a potato baton into the oil. Look for gentle bubbling, not an aggressive sizzle.
3. Fry the potatoes in batches for about 3 minutes each. Transfer each batch to a paper towel-lined tray; the fries will still be pale at this stage. Reheat the oil to 275°F (135°C) before adding the next batch.
4. Let all the fries cool for at least 30 minutes (they can sit uncovered at room temperature for a few hours).

Make the Garlic-Herb Compound Butter

1. Cut the butter into small cubes, place them in a bowl, and let them soften at room temperature. To speed this up, microwave it in a microwave-safe bowl in 5-second bursts until soft but not melted.
2. Add the rosemary, parsley, garlic, salt, and black pepper. Mash and mix with a fork until well combined, then taste and adjust the seasoning.
3. Cover and refrigerate until ready to use.

Cook the Steak

1. Once the compound butter is ready, the fries are blanched and cooled, and the steak has finished dry-brining, take the steak out of the refrigerator about 15 minutes before cooking.
2. Turn on the exhaust fan or open a window. Heat a heavy skillet over medium-high heat for about 3 minutes. Add 2 tablespoons of high-smoke-point oil and heat for another minute. At the same time, start heating the oil for the fries’ final fry.
3. Pat the steak dry with paper towels. Place it in the hot skillet and sear, flipping every 30 seconds, until it reaches the pull temperature for your preferred doneness:
   105°F (41°C) for rare,
   115°F (46°C) for medium-rare,
   125°F (52°C) for medium,
   135°F (57°C) for medium-well,
   145°F (63°C) for well-done.
   See the complete steak temperature chart below.
4. Transfer the steak to a serving plate, top with 1 to 2 tablespoons compound butter, and rest for 5 minutes.
5. While it rests, finish the fries.

Second-Fry the Fries at 350°F (180°C)

1. Heat the oil to 350°F (180°C).
2. Fry the blanched fries in batches for about 3 minutes, until golden and crisp.
3. Use a skimmer or large slotted spoon to transfer each batch to a paper towel-lined bowl or tray. Let the oil reach 350°F again before adding the next batch.
4. Once all the fries are done, season generously with salt and serve right away.

Serve the Steak and Frites

1. Add the hot fries alongside the steak and any sides you like. For coarse-grain cuts, such as flank, hanger, or outside skirt, slice thinly against the grain. Serve right away while the steak is warm and the fries are still crisp.

Steak Temperature Chart