Seared Lamb with Mustard Potatoes and Green Beans

Heat the oven to 400 degrees F. Place the potatoes in a medium pot and cover with cold water. Bring to a boil, then reduce heat and cook until just tender, 12 to 15 minutes, adding the green beans during the last 3 minutes of cooking. Drain, reserving 1/4 cup cooking liquid. Cut the potatoes in half (or quarter if large). Return the vegetables to the pot and toss with the mustard and 1 tablespoon cooking liquid (adding more water, 1 tablespoon at a time, if the potatoes seem dry). Meanwhile, heat 1 tablespoon oil in a large ovenproof skillet, season the lamb chops with 1/4 teaspoon each salt and pepper and cook until golden brown, 2 minutes per side. Transfer the skillet to the oven and roast to desired doneness, 4 to 6 minutes for medium-rare. While the lamb is cooking, using a vegetable peeler, remove 4 strips of lemon zest and finely chop. In a bowl, combine the zest, garlic, bread crumbs, and remaining tablespoon oil. Scatter evenly on a small rimmed baking sheet and toast until golden brown, 3 to 4 minutes. Squeeze 2 tablespoon lemon juice over the bread crumbs, sprinkle with the parsley and 1/4 teaspoon each salt and pepper, and toss to combine. Spoon over the lamb and serve with the potatoes and green beans.