How to Make It
Holding salt about 1 foot above steaks, sprinkle both sides of steaks evenly with salt in a steady stream, pressing slightly to adhere. Place steaks on a wire rack set inside a rimmed baking sheet. Chill, uncovered, 72 hours, turning twice a day.
Remove steaks from refrigerator. Let stand 1 hour. Preheat oven to 400°F. Heat oil in a 12-inch cast-iron skillet over high. Sprinkle steaks evenly with pepper. When a wisp of smoke rises from skillet, add steaks in a single layer, and cook, undisturbed, until a light brown crust forms, about 4 minutes. Flip steaks, and cook 4 minutes. Using tongs, turn steaks on fatty edges, leaning steaks against sides of skillet to keep them stable, if needed. Cook, rolling occasionally to render fat on edges, until caramelized all over, 4 to 5 minutes. Place steaks flat in skillet, and add butter and garlic around steaks.
Transfer skillet to preheated oven. Roast steaks 5 minutes. Transfer skillet to stovetop over medium. Slightly tilt skillet toward you so butter pools in bottom of skillet; spoon brown butter over steaks. Carefully flip steaks, and baste again. Return skillet to oven, and roast until a thermometer inserted in thickest portion registers 120°F, 4 to 6 minutes.
Transfer steaks to a cutting board, and let rest 10 minutes. Remove bones, and separate fatty strip from each steak. Slice steak thinly against the grain, and reassemble steaks on a platter, fanning slices out slightly. Arrange bones on plates; sprinkle steaks with sel gris.
Try this method with any well-marbled cut of red meat: prime rib (increase cook time), T-bone steaks, or pork shoulder steaks.