Step 1

Preheat the oven to 450°. In a small bowl, mix the mustard with the garlic, thyme, pepper and 2 teaspoons of kosher salt. Whisk in the olive oil.

Step 2

Set the meat, bone side down, in a roasting pan and season it lightly with salt. Roast the meat in the lower third of the oven for 20 minutes.

Step 3

Remove the meat from the oven and reduce the temperature to 350°. Brush the mustard coating all over the top and sides of the meat and roast for about 1 1/2 hours longer, rotating the roasting pan 2 or 3 times for even browning. The meat is done when an instant-read thermometer inserted in the center of the roast at the thickest part registers 120° (for medium rare). Transfer the roast to a carving board, cover it loosely with foil and let rest for 20 to 30 minutes.

Step 4

Set the roast on its side and run a long, sharp knife between the bones and meat; remove the bones and set them aside. Turn the roast right side up. Carve the roast 1/4 to 1/2 inch thick and transfer the slices to warmed plates. Pour any carving juices over the meat and serve at once. For bone-gnawing carnivores, cut down between the rib bones and pass them on a plate.