Source: Martha Stewart Living
adapted by http://theresalwaysthyme.blogspot.com/
1/2 cup (1 stick) unsalted butter, softened
1 fresh jalapeno chile, seeded and finely chopped
1 clove garlic, minced
1 porterhouse steak (2 1/2 pounds, 1 1/2 inches thick), room temperature
Coarse salt and freshly ground pepper
Preheat grill to medium-high.
Stir butter, jalapeno, and garlic in a bowl; set aside.
Season both sides of steak with salt and pepper. Grill over hotter part of grill, covered, flipping once, until browned, 3 to 4 minutes per side. Slide to cooler part of grill; grill, covered, flipping once, until medium-rare, 7 to 8 minutes more per side. Remove from grill, and let rest 10 minutes. Serve with jalapeno butter.