Heat a large nonstick skillet coated with cooking spray over medium-high heat. Sprinkle steaks with 1/4 teaspoon salt and pepper. Add steaks to pan; cook 3 minutes on each side or until desired degree of doneness. Remove from pan; keep warm.
Add dry white wine, sugar, and Dijon mustard to pan; bring to a boil. Cook 1 minute, stirring constantly. Remove from heat. Stir in 1/4 teaspoon salt, sour cream, and chopped tarragon. Spoon sauce over warm steaks. Garnish with tarragon sprigs, if desired.