For the lamb marinade and sausages: Combine the oil, vinegar, honey and mustard in a large resealable plastic bag. Season with salt and pepper. Add the lamb to the bag and marinate in the refrigerator for at least 3 hours (or overnight).
Preheat the oven to 350 degrees F (180 degrees C).
Heat a heavy ovenproof skillet over high heat until hot. Meanwhile, pat the lamb dry and discard the marinade. Add the oil to the hot skillet, then brown the racks of lamb
on all sides, about 3 minutes. Add the sausages, shallots and rosemary to the skillet and sprinkle with salt and pepper.
Transfer the skillet to the oven and cook until a meat thermometer
inserted into the center of the lamb registers 140 degrees F (60 degrees C), about 25 minutes. Transfer the lamb and sausages to a platter and cover with foil to keep warm and allow the juices to redistribute. Discard the shallots and rosemary and reserve the skillet.
For the sauce: Add the veal stock
to the skillet and bring to a simmer, stirring and scraping up any browned bits from the bottom with a wooden spoon. Let the sauce reduce for about 5 minutes or until it reaches the desired consistency. Whisk
in the butter, if using, and season with salt and pepper.
Slice the lamb between the bones and serve with the sausages
, Crispy Potatoes, a ladle of the sauce and a dollop
of Spicy Red Pepper Jelly.