The porterhouse is a composite steak coming from the point where the tenderloin and top loin meet. It is basically an over-sized T-bone steak, but the porterhouse is generally cut thicker and has much more of the tenderloin relative to the loin portion than a T-bone steak. If you remove the bone and cut out the two steaks that make up the porterhouse, you will get a tenderloin steak and a top loin (or New York strip steak). So if you are ordering a porterhouse, expect big portions. A good porterhouse is also the perfect steak for two people to share.
Buying a Porterhouse
When buying a porterhouse steak, look for one cut at least 3/4-inch thick, with a 1-inch thickness being ideal. Occasionally, butchers will sell "thin" cut steaks, and these are largely pointless. A porterhouse should be thick, and not just because it is a huge steak and deserves to be so. To get a large steak like this cooked to perfection without it drying out, it needs to have mass and thickness.
A good porterhouse should have a deep, rich color without any gray. The fat should be white and not yellow. Look for good marbling throughout the meat, particularly the loin portion. Don't try to get a bargain on a steak like this. While dry aged and/or prime grade versions of the porterhouse will be expensive, you can find a good "choice" grade steak that is fresh and very flavorful.
Cooking a Porterhouse
Since both the loin and tenderloin are quite forgiving, a porterhouse steak can be cooked any way you like. It is perfect when grilled, but can also be broiled, sauteed, or pan-fried. Use light seasoning with a good amount of salt and try not to cook it beyond medium-well at the very most.
To grill a porterhouse, start hot and fast, giving the surface a good sear. Cook to the point right before the fat would start to burn, then flip it over on the other side. To get those restaurant-style diamond grill marks, rotate it 45 degrees on the same side before flipping and repeating on the other side.
Once it is well browned on both sides, move it to a cooler part of the grill to finish off to the desired doneness. To give it an extra richness, place a pad of butter in the center of the steak a few minutes before removing from the grill. This is a popular restaurant trick that brings out the flavor.
One way to grill porterhouse is as a cowboy steak. Give it a southwestern twist by seasoning it with a paste that includes garlic, chili powder, chipotle powder, salt, and pepper. Wrap it in plastic and refrigerate it for a few hours so it absorbs the spices before grilling.
Serving a Porterhouse Steak
A porterhouse can be served whole or sliced, depending on how you want to divide it up. For the very hearty appetite, it is a tremendous meal, a challenge even. As a steak for two, this makes the perfect "special occasion" steak.