Melt the butter in a large stockpot over medium heat. Add the onions, leeks, celery and sugar and saute for 10 minutes, until carmelized and golden brown. Add the thyme, basil, bay leaves, salt, pepper and cayenne and stir to coat the vegetables. Add the stock and canned tomatoes, bring the mixture to a boil, reduce heat, partially cover and simmer for 30 minutes. Stir in heavy cream and brandy and simmer for 2 minutes. Remove the bay leaves and puree about half of the soup in a blender or food processor until smooth. Return the puree to the pot and heat through. Remove from the heat and stir in the plum tomatoes and garlic. To serve, ladle the bisque into bowls and top with chopped chives.
Combine all the ingredients in a large stockpot. Bring to a boil over medium-high heat. Reduce heat, partially cover and simmer for one hour. Strain the stock and discard solids.