Preheat the oven to 450 degrees F.
Rub lamb racks with olive oil. Rub with mustard, basil, thyme, and oregano. Season with salt and pepper. Sear, fat side down, in a saute pan until brown, about 5 minutes. Put in the oven for 15 minutes for medium rare.
Put the potatoes on 4 plates and arrange a half rack of lamb on top. Drizzle entire dish with port wine demi-glace.
Boil the potatoes until fork tender. Drain. Mash and season with garlic, salt, and pepper.
In sauce pot, over medium high heat, reduce the wine to 1 tablespoon liquid. Add the veal stock and reduce by 2/3. Season with salt and pepper. Strain.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.