In large heavy saucepan, melt butter over medium heat. Cook potatoes, celery, carrot, onion and garlic, stirring for 8 minutes or until soft. Stir in flour. Gradually whisk in 5 cups of stock.
Bring to boil. Reduce heat and simmer, covered for 10 minutes or until tender. In separate saucepan bring remaining stock (1 cup) to boil. Reduce heat to simmer and poach salmon for 1 minute. Remove with slotted spoon and set aside. Poach scallops 1 minute and add to salmon.
Poach mussels, covered, for 3 minutes, discarding any that don't open. Strain poaching liquid into vegetable mixture. Add cream, dill, basil and pepper. Heat. Add reserved seafood. Heat until steaming.Servings: 6