Rub the fat side
of each rack of lamb with the mustard. In a skillet, cook the
shallot in butter over moderately low heat, stirring for 2
minutes and remove the skillet from the heat.
Add the thyme, bread crumbs, and salt and pepper to taste
and toss the mixture well. Let the mixture cool down and
stir in the parsley. Season the lamb with salt and pepper,
pat the crumb mixture evenly over the mustard, and arrange
the lamb crumb side up in a roasting pan.
Roast the lamb in a preheated 450-degree (F) oven for 30
minutes, or until a meat thermometer registers 130 to 135
degrees (for medium-rare meat). Transfer the lamb carefully
to a work surface and let it stand for 10 minutes. Interlock
the ribs together carefully and transfer the lamb to a platter.
Garnish the platter with rosemary sprigs.
Serves 4 generously.