To prepare the racks of lamb: Heat the vegetable oil in a saute pan over high heat. Season the racks of lamb with salt and pepper (I use fresh ground sea salt and ground white pepper). Sear the racks on all sides until nicely browned. Remove racks to a platter and allow to cool enough to handle. At this point preheat the oven to 400 degrees F.
To make the walnut crust: Put dried rosemary into a food processor and pulse several times to grind, If you don't do this the rosemary pieces will be too large. Add walnuts, 1/4 teaspoon of salt and 1/2 teaspoon of white pepper, and garlic powder. Pulse several times until mixture is the consistency of bread crumbs. Pour mixture onto a large dinner plate or a platter.
To make the mustard mixture: In a dish combine the egg, mustard and 2 cloves of minced garlic. Mix well with a fork until egg and mustard are completely incorporated.
To coat the racks of lamb: Line a baking sheet with parchment paper or foil. Once the racks are cool enough to handle, place 1 rack in the mustard mixture and coat all sides. Next place the coated rack into the walnut mixture and coat well. Using your hand press the walnut mixture firmly onto the coated rack. Transfer rack to the baking sheet. Repeat steps for each rack. You can make the recipe to this point and place in refrigerator until ready to cook.
To cook: Place the racks of lamb into the oven and roast for 20 minutes for medium rare. I use a temperature probe in one of the racks, and remove meat from oven when it registers between 125 to 130 degrees F. Remove from oven and let stand for 5 to 10 minutes before cutting.
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.