Pour off any fat from cooking the steak. Melt butter in the same skillet over low heat; add onion and garlic and cook slowly until soft. Add remaining ingredients and simmer for a minute or two. Pour over steaks. Trim excess fat from outside the steak. Press crushed peppercorns and garlic into both sides of the meat and let stand at room temperature for 1 hour. Heat a cast-iron skillet over high heat. Grease the bottom of the hot skillet with a piece of fat trimmed off the steak. Toss in about half of the salt. Sear the steak or steaks quickly on one side, then lift out, add the remaining salt to the skillet, turn the steak, and sear the other side. Reduce the heat to medium and cook the steaks as desired. Remove to a warm platter. Pour sauce over steaks and serve.
PER SERVING: 700 calories, 44 g protein, 1 g carbohydrate, 55 g fat, (28 g saturated), 196 mg cholesterol, 613 mg sodium, 0 g fiber.