Marinate the lamb with the olive oil, garlic and rosemary. Season on both sides with salt and pepper and refrigerate overnight.
To make the spice mixture, place the hazelnuts on a pie tin and roast in the oven until the skins begin to darken, about 8-10 minutes. Remove from the oven and place in a fine mesh strainer with a lightly damp towel on top. Rub the towel against the nuts to remove the dark skin that covers the hazelnuts. Don’t worry if not all the skin comes off. Roughly chop on a cutting board and set aside.
Toast the sesame seeds in a hot skillet over high heat for a minute or two, stirring constantly to evenly brown. Remove from the skillet and set side. Place the coriander and cumin in the skillet and toast for a minute or two until fragrant and starting to darken. Coarsely grind the spices with a mortar and pestle or pulse in spice mill. Add the hazelnuts and pound a few times with the pestle to incorporate into the spices. Stir in the sesame seeds, salt and freshly ground black pepper. Place in a shallow dish or pie tin.
Heat oven to 400˚F. Remove the lamb from the refrigerator and allow to come to room temperature. Heat the vegetable oil in a large skillet over high heat. Add the lamb racks, fatty side down first. Using a pair of tongs flip and brown the bottom and back of the rack, until the crust is browned, about 10 minutes. Remove from the skillet and brush with Dijon mustard. Roll in the nut and spice mixture and transfer to a resting rack set in a sheet pan. Cook in the oven until a meat thermometer inserted into the center of the thickest part of the meat reads 130˚F approximately. Remove from oven and let cool for 5 minutes before slicing into chops and serve.
Enjoy with a glass of Cakebread Cellars Nap Valley Merlot.