Heat a large nonstick skillet coated with cooking spray over medium-high heat; add oil. Add shallots and garlic; sauté 3 to 5 minutes or until tender.
Add wine, broth, and lemon juice; bring to a boil. Add fish; cover, reduce heat, and simmer, 12 to 14 minutes or until fish flakes easily when tested with a fork. Remove fish; set aside and keep warm.
Bring liquid to a boil; cook, uncovered, 3 minutes or until liquid reduces to 3/4 cup. Stir in mustard and capers. Spoon sauce over fish, and serve immediately.