Bring 4 quarts water to a boil in a Dutch oven, and stir in juice. Add cauliflower, reduce heat, and simmer 15 minutes or until tender. Drain.
Melt 1 1/2 teaspoons butter in a large nonstick skillet coated with cooking spray over medium heat. Add leek and salt; cover and cook 5 minutes, stirring occasionally. Reduce heat to medium-low; cook 5 minutes or until tender (do not brown), stirring occasionally. Combine leek and cauliflower.
Place half of cauliflower mixture and 1 cup broth in a blender; process until smooth. Pour puréed mixture into a large bowl. Repeat procedure with remaining cauliflower mixture and 1 cup broth.
Melt 1 tablespoon butter over medium heat in Dutch oven. Cook 3 minutes or until lightly browned, stirring occasionally. Add cauliflower puree and remaining broth. Simmer 5 minutes. Stir in pepper and nutmeg. Sprinkle each serving with 1/2 teaspoon chives.