Combine carrots, water, bay leaf, if using, and garlic in a medium-sized pot. Bring to a boil.

Reduce heat, cover, and simmer for 20 minutes. Remove and discard bay leaf. Using a hand blender or food processor, blend carrot mixture until smooth.

In a soup pot, place flour; gradually add milk or soy milk, stirring until well blended. Stir in pureed carrots and nutmeg. Bring to a boil.

Remove from heat and stir in butter or margarine, salt, and lemon juice.