In a medium casserole, sweat leeks, onions, and garlic in olive oil for 10 minutes. Add mussels, brandy, and wine and cover and steam mussels until they open. Remove from heat. Separate mussels from shells and place mussel meat in sauce pan. Add tomatoes and 4 ounces of water. Season with salt and pepper, bring to a boil, and let simmer for 10 minutes. In a food processor, puree until smooth. Strain through a sieve. Add additional water if bisque appears too thick. Whisk in olive oil, butter and additional salt and pepper, to taste.