Coat a foil-lined baking sheet with cooking spray. Place lamb on prepared pan. Sprinkle lamb evenly with 1/2 teaspoon pepper, 1/4 teaspoon salt, and thyme. Broil 5 minutes on each side.
Combine juice, mustard, and honey in a small bowl. Heat a small saucepan over medium-high heat. Coat pan with cooking spray. Add shallots and garlic to pan; sauté 1 minute. Stir in juice mixture; bring to a boil. Reduce heat and cook until reduced to 1/2 cup (about 5 minutes). Combine cornstarch and water in a small bowl; stir until smooth. Add cornstarch mixture to pan; bring to a boil. Cook 1 minute, stirring constantly. Remove from heat; stir in chives, 1/8 teaspoon salt, and 1/8 teaspoon pepper. Serve with lamb.