The basic concept is that you assemble a large cast-iron sautoir or sauteuse and a footed rack that will fit in it. The resulting combination becomes a quick way to produce a steak and "fried" or "roasted" potatoes meal with a minimum of hassle and cooking pans. To make it work:
Pre-heat the oven to 450 degrees. Cut up the potatoes (any shape - doesn't have to be the slices shown here) and boil them for 10 minutes. Drain and set aside. Heat the saute' pan, without the rack, to about 350 surface temperature (you do have a infrared surface thermometer , don't you?), and sear your steak on both sides. I typically sear it for 4 minutes a side -- leave it longer if you want more carmelization.
Turn off the burner and remove the steak from the pan. Add the potatoes, and set the rack on top of them. Place the steak on the rack, and put the whole thing, uncovered, in the oven. Check internal temperature of the steak at 10 minutes and at intervals thereafter. When it's as done as you want it (130 degrees will coast up to medium rare with 10 to 15 minutes resting time), remove the steak to a platter to rest and the potatoes to a serving dish.
The mechanism is pretty simple; a steak (or cote de boeuf or even rack of lamb, for that matter) will render fat while it's finishing in the oven this way. Instead of it sitting there in all that oil, deep-frying itself, this method keeps the meat up above the pan surface and lets the potatoes benefit from all that flavorful juiciness.
