The small, pale green kidney-shaped beans called flageolets are a classic accompaniment for lamb in traditional French cuisine.
FOR THE LAMB:
2 long branches rosemary
8 sprigs thyme and a handful of thyme branches
4 cloves garlic, smashed and peeled
2 tbsp. extra-virgin olive oil
1 tsp. cracked black pepper
2 racks of lamb (12 chops in all), fat trimmed from bones
2 medium yellow onions, peeled and cut into wedges
1 head garlic, halved
FOR THE FLAGEOLET GRATIN:
2 small yellow onions, peeled
2 tbsp. extra-vrigin olive oil
1 small fennel bulb, trimmed and diced
2 garlic cloves, smashed and peeled
1 cup flageolets
1/2 tsp. fresh thyme leaves
1 bay leaf
1 chille de árbol or other dried chile
3 tbsp. butter
1/2 cup fresh bread crumbs
2 tbsp. brown butter
1/2 tsp. chopped fresh parsley
1. For the lamb: Mix together the leaves from 2 sprigs of the rosemary, 8 sprigs of the thyme, garlic cloves, oil, and pepper in a small baking dish, then rub the mixture all over the lamb racks. Cover with plastic wrap and refrigerate overnight.
2. For the flageolet gratin: Preheat oven to 400°. Dice half of 1 onion and sauté in oil with fennel and garlic in an ovenproof pot over medium heat until vegetables are soft, about 5 minutes. Stir in flageolets, cook for 2–3 minutes, then add thyme, bay leaf, chile, and 3 cups water. Bake, covered, until tender, about 1 hour. Season to taste with salt halfway through cooking (add more water if beans dry out). Set aside to cool (remove and discard bay leaf and chile). Leave oven on.
3. Thinly slice remaining 1 1/2 onions and sauté in butter in a medium pan over medium heat until golden, about 15 minutes. Spread onions in the bottom of a 6'' X 6'' baking dish, then spoon in flageolets with some of their cooking juices. Toss bread crumbs with brown butter and parsley, sprinkle over beans, and return to oven for 20 minutes.
4. Season lamb with salt, then sear on all sides in a cast-iron pan over high heat, with rosemary branches, broken into a few pieces, and thyme branches. Scatter onions and garlic in a roasting pan, put lamb on top, and roast in oven for 20–25 minutes. Set lamb aside to rest for 5 minutes. Remove flageolets from oven when bubbling and golden, and divide between 4 plates. Slice each rack into 6 chops, place 3 chops on top of each serving of flageolets, and spoon some tapenade over the meat.