Brown meat in olive oil in fireproof casserole or Dutch oven. Add onion and garlic and cook until soft. Blend in salt and flour, stir until smooth. Add remaining ingredients except chocolate. Cover and simmer gently 2 1/2 to 3 hours. Remove meat, add chocolate to sauce and cook until thickened and smooth. If much liquid has cooked away, add water to make about 2 cups. Add salt to taste.