It is necessary to trim almost all the fat from the lamb (leave a very thin layer) to ensure that the crust becomes sufficiently crisp. Make sure to use white miso paste. The red variety is very salty and the flavour can be overpowering. You can purchase white miso paste at most Asian grocery stores. The miso must be added to the sauce at last minute as it loses its flavour if it is heated or sits.Chicken or veal stock that is homemade or good-quality store-bought stock is ideal here, as opposed to canned stock which is too salty with the miso paste. If canned stock is your only option, use the low-sodium variety. Yield is 4 servings.
Preheat the oven to 400 degrees F.
To prepare the racks of lamb, mash garlic and herbs to a paste with a mortar and pestle.
Trim excess fat from lamb, leaving a thin layer.
Score fat in a crisscross pattern, being careful not to score the meat.
Season lamb with salt and pepper.
Heat a large saute pan on medium-high heat until smoking.
Sear lamb, backbone side down, for about 1 minute.
Sear lamb on fat side for 2 to 3 minutes or until golden and crispy.
Rub the fat side of the lamb with 2 tsp. of the miso paste.
Press on the Panko mixture.
In the same saute pan, sear the lamb again, fat side down, until panko crust is golden and crisp, about 2 minutes.
Turn lamb and put it in the oven. Roast for 20 to 25 minutes until medium rare or until desired doneness.
Let rest for 5 to 10 minutes.
Heat olive oil in a small saucepan over medium-low heat.
Add the shallots and cook for about 4 minutes, until softened.
Deglaze pan with the Sauternes and simmer until reduced by half, about 30 seconds
Add the stock and the thyme sprigs.
Simmer until reduced by half, about 15 minutes.
Whisk in remaining miso paste and remove from the heat. Please note that the miso paste must be added at the last minute and taken off the heat as it loses its flavour if it is heated or sits.
Slice lamb and serve with the sauce.
Garnish with thyme sprigs.