1. 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.
2. 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.
Make Ahead: The cooked steak can be refrigerated overnight.
Wine Recommendation: A young California Zinfandel with lots of spice and fruit would pair best with this cured steak. Try the 1997 Geyser Peak Winemaker's Selection or the 1996 St. Francis Reserve Pagani Vineyard.