Arrange asparagus and potatoes on baking sheet and spray with cooking spray. Season with salt and black pepper. Roast 20 to 25 minutes, until tender and golden brown.
Meanwhile, season lamb chops all over with salt and black pepper. Heat oil in a large skillet over medium heat. Add chops and sear 2 to 3 minutes per side, until golden brown. Remove lamb from pan and set aside. Add leeks to the same pan and saute 3 minutes, until soft. Return lamb to pan.
In a small bowl, whisk together plum sauce, plum preserves and rosemary. Pour mixture over lamb chops. Simmer 5 minutes, until lamb is tender and medium-rare to medium.
In a small bowl, whisk together lemon juice, lemon zest, oil and mustard. Season to taste with salt and black pepper. Arrange asparagus on a serving dish. Drizzle lemon vinaigrette over top. Top with diced egg. Serve lamb chops with asparagus and potatoes on the side and extra sauce (with leeks) spooned over top.