Sprinkle both sides of lamb with 1/4 teaspoon each salt and pepper. Coat a large nonstick skillet with cooking spray; place over medium-high heat until hot. Add chops; cook 3 minutes on each side. Reduce heat to medium; cook 4 minutes on each side or until desired degree of doneness. Set aside; keep warm.
Add half of butter to skillet; cook over medium-high heat until butter melts. Add sweet potato, and cook 3 minutes or until tender, stirring often. Set aside, and keep warm.
Add remaining butter, shallots, and garlic; cook, stirring constantly, 2 minutes. Increase heat to high, and add balsamic vinegar. Simmer until liquid is almost evaporated. Add chicken broth and sugar; simmer 3 minutes. Add reserved sweet potato, Dijon mustard, thyme, tarragon, and remaining 1/4 teaspoon each salt and pepper; stir well. Spoon sauce over chops.