Preheat oven to 375°.
Combine first 4 ingredients in a small saucepan; bring to a boil, stirring occasionally. Cook until reduced to 3 tablespoons (about 5 minutes). Remove from heat; stir in vinegar.
Arrange fish on a broiler pan coated with cooking spray. Brush fish with half of sherry mixture. Bake at 375° for 5 minutes; brush fish with remaining sherry mixture. Bake an additional 5 minutes or until fish flakes easily when tested with a fork.
While fish bakes, combine water and next 6 ingredients (water through pepper) in a large skillet over medium-high heat; bring to a simmer. Add greens; cover, reduce heat to medium, and cook 10 minutes or until tender.