Melt 2 tablespoons butter in a large, heavy pot over medium heat. Add onions, potatoes, and grated carrot. Saute until soft, about 5 minutes. Remove and put in bowl.
Add remaining 4 tablespoons of butter to the same pot. Add flour and whisk constantly over medium heat until roux becomes light brown, about 5 minutes. Stir in seafood broth, whisking constantly to make sure soup stays smooth.
Add sauteed onions, potatoes, and carrot; cover and simmer for 10 minutes. Add cream, sherry wine, lemon juice, Worcestershire sauce, and crabmeat and simmer 5 more minutes.
Replace crab with either lobster, shrimp or clams.
Nutrition Facts (per serving): Calories 430 Fat 19 g Carbohydrate 42 g Fiber 3 g Sugars 5 g Protein 22 g Sodium 1680 mg Potassium n/a (not available for Campbell's product) Calcium 180 mg