First you make a roux, which is the 6 tablespoons of flour poured into 3 tablespoons of hot olive oil and cooked until you have a darkened paste.
Soak the olives in cold water for 1 hour. Drain and coarsely chop the olives. Heat a frying pan and add 3 tablespoons of oil, onion, and garlic, along with 2/3 of the olives. Saute until the onions are transparent. Puree the mixture in a food processor along with 1 cup of the stock. Place this mixture into a 4 quart saucepan and the rest of the stock. Simmer for 20 minutes and add cream. Whisk in the roux and simmer, stirring constantly until thickened. Add pepper to taste and remaining chopped olives, Tabasco, and sherry.