Melt the butter in a medium-sized pot set over medium heat. Add the leek, carrot and garlic and cook 3-4 minutes. Mix in the flour and cook 1-2 minutes more. Slowly, stirring steadily, pour in the stock. Bring the soup to a gentle simmer, and then adjust the heat downward to maintain that gentle simmer. Add the smoked salmon, potatoes and bay leaf and cook until the potatoes are just tender, about 10 minutes. Mix in the scallops and dill and cook 3-4 minutes more, or until the scallops are just cooked through. Mix in the cream and heat through 1 minute. Season with salt and pepper and serve.