Grilled Porterhouse Steak

3 (1 1/2-inch-thick) porterhouse steaks (each about 2 to 2 1/4 pounds)
3 tablespoons mixed whole peppercorns
1 1/2 teaspoons coarse salt
Horseradish-Mustard Butter, sliced into 6 rounds, recipe follows
Prepare grill.

Let steaks stand at room temperature 30 minutes. With a mortar and pestle or bottom of a heavy skillet coarsely crush peppercorns and in a small bowl combine with salt. Pat steaks dry and rub seasoning onto both sides of steaks, pressing to adhere.

Grill steaks on an oiled rack set 5 to 6 inches over glowing coals 7 to 9 minutes on each side, or until an instant-read thermometer registers 130 degrees F. for medium-rare. (Alternatively, steaks may be broiled on rack of a broiler pan under a preheated broiler about 4 inches from heat.) Transfer steaks to a platter and let stand 10 minutes.

Serve steaks sliced with the horseradish-mustard butter.

Horseradish-Mustard Butter:
6 tablespoons unsalted butter, softened
3 tablespoons drained bottled horseradish
3 tablespoons Dijon mustard
1 1/2 tablespoons minced shallot
Kosher salt and freshly ground black pepper, to taste

In a bowl, blend together the butter, horseradish, mustard, and shallot with a fork.
Season with salt and pepper. On a sheet of plastic wrap, form the butter into a log about 4 inches long. Chill the compound butter until firm, at least 30 minutes or freeze until ready to use.