- 2 (1 1/4-inch-thick) porterhouse steaks (4 pounds total)
- 1 cup sour cream
- 1/4 cup undrained horseradish (from a new jar)
- 4 scallions, chopped
- 1 1/2 teaspoons salt
- 1 1/2 teaspoons black pepper
- Special equipment: an instant-read thermometer
- Prepare grill for cooking over direct heat with medium-hot charcoal (moderate heat for gas).
- While coals are lighting, let steaks stand at room temperature about 15 minutes. Stir together sour cream, horseradish, scallions, 1/2 teaspoon salt, and 1/2 teaspoon pepper in a bowl.
- Pat steaks dry and sprinkle all over with remaining teaspoon each of salt and pepper. Grill steaks on lightly oiled grill rack, covered only if using a gas grill, turning steaks over once and moving them around grill to avoid flare-ups if necessary, until thermometer inserted horizontally 2 inches into meat (do not touch bone) registers about 120°F for rare, 9 to 12 minutes total. Transfer steaks to a cutting board and let stand 10 minutes before slicing. (Internal temperature will rise to 125 to 128°F while steaks stand.) Thinly slice meat and serve with sauce.