Melt the butter in a pot over medium heat. Add the onion, celery and garlic and cook until tender, about 5 minutes. Sprinkle in the flour and mix well. Slowly stir in the stock. Bring to a boil, and then reduce the heat to a gentle simmer. Add the bay leaf, potatoes, smoked salmon and halibut and cook until the potatoes are just tender, about 10-15 minutes. Stir in the cream and dill and gently simmer a few minutes more. Season with salt and pepper and serve.