My butcher had gone home early, so I couldn't get the two-inch porterhouse I usually ask for (I have them cut special). Instead I settled for two one-inch porterhouses that I cooked separately.
So I slathered them with a mix of canola oil and melted butter; sprinkled them with lots of kosher salt and fresh-cracked pepper, then cooked them, one at a time, four minutes to a side, in a cast-iron pan that had been heating in a 500 degree oven for half an hour.
While the steaks rested for about five minutes, I sprinkled a handful of fine-chopped onions into the pan (I forgot to buy shallots), cooked em for 30 seconds, then poured in half a cup of balsamic vinegar (the good stuff, really sweet), and reduced it over medium heat until there was about a couple of tablespoons left. Took it off the heat, Dropped three tablespoons of butter into the sauce to melt, and served it with the steaks.
The quiet tart-and-sweet of the reduced balsamic and the rich velvety nuttiness of the butter gave the porterhouse a lovely flavor. We ate it with hot and crusty French bread and a salad of mixed greens dressed with extra virgin olive oil, lemon juice, a crushed garlic clove, kosher salt and cracked black pepper.