How to Make It
In a medium skillet, toast the coriander and mustard seeds, peppercorns and fenugreek over moderate heat until fragrant, about 1 minute. Transfer to a work surface to cool. Using the side of a chef's knife, coarsely crush the spices. Put the crushed spices in a bowl and add the garlic, kosher salt, brown sugar and ginger. Rub the mixture onto both sides of the steak and put the meat in a sturdy plastic bag. Refrigerate for at least 18 and up to 24 hours.
Scrape the seasoning mixture from the steak. Set a large cast-iron skillet over moderate heat for 3 minutes. Raise the heat to moderately high, add the oil and heat until almost smoking. Add the steak and cook until well-browned on the bottom, about 4 minutes. Lower the heat to moderate, turn the steak and cook until browned on the bottom, about 4 more minutes for medium rare. Transfer the steak to a cutting board and let rest for 5 minutes. Thinly slice the meat across the grain and serve.