Instructions

1. Place 12 ounces small gold potatoes in a medium saucepan and add enough cold water to cover the potatoes by about an inch. Stir in 1 tablespoon of the kosher salt and bring to a boil over high heat. Reduce the heat as needed to maintain a lively simmer and cook until the potatoes are knife-tender, about 20 minutes. (This is a good time to prep the remaining ingredients.)
2. Drain the potatoes. Using a flat spatula or the back of a spoon, gently press on each potato until the skin cracks and they have flattened slightly.
3. Pat 1 (1-pound) steak dry with paper towels and season all over with the remaining 1 teaspoon kosher salt. Heat a medium cast-iron or stainless steel skillet over high heat until it starts to smoke. Add 1 tablespoon neutral oil and 1 tablespoon unsalted butter, then add the steak and cook until medium-rare and a brown crust forms, 3 to 4 minutes per side (an instant-read thermometer inserted into the steak should register about 130°F). If your steak has a fat cap, stand it on its side with tongs and cook until browned, adjusting the angle as needed, about 1 minute. Transfer the steak to a clean cutting board and cover with aluminum foil.
4. Add the cooked potatoes to the skillet. Cook until golden brown on both sides, flipping halfway through, about 5 minutes total. Transfer to a large bowl.
5. Reduce the heat to medium. Add 1 tablespoon unsalted butter, 1 finely chopped medium shallot, 2 thinly sliced garlic cloves, and 1 tablespoon coarsely crushed peppercorns to the same pan (no need to clean). Cook, stirring frequently, until the shallots are softened, about 3 minutes. Remove the pan from the heat.
6. Add 1/4 cup Cognac and 2 teaspoons white miso paste to the pan. Return to medium heat and simmer, scraping up any browned bits stuck to the bottom of the pan, until mostly evaporated, 1 to 2 minutes.
7. Stir in 1/2 cup heavy cream, 1 teaspoon Dijon mustard, and 1 teaspoon maple syrup. Bring to a simmer, stirring constantly, until the sauce thickens enough to coat the back of a spoon, about 1 minute. Stir in the accumulated juices from the steak cutting board. Taste and season with kosher salt as needed.
8. Add 4 packed cups hearty salad greens, 1 thinly sliced medium shallot, and 4 thinly sliced small radishes to the bowl of potatoes. Drizzle with 2 teaspoons sherry vinegar and gently toss to coat and evenly mix. Transfer to a serving platter.
9. Cut the steak across the grain into 1/2-inch thick slices. Shingle or spread evenly over the salad. Spoon some of the peppercorn sauce over the steak and salad. Garnish with finely chopped fresh chives. Serve the rest of the peppercorn sauce on the side for spooning over as you eat.