In a medium-size mixing bowl, combine the blue cheese, lemon juice, Worcestershire, hot sauce, salt and black pepper. Using the back of a fork, mash the mixture together to form a thick paste. Drizzle in the oil, stirring continuously with the fork until the mixture is creamy. Add the buttermilk and mix well. Cover and refrigerate for 1 hour. Season both sides of the tomatoes with salt and pepper. To serve, place a tomato in the center of each plate. Drizzle some of the dressing over the tomato. Place some of the sliced onions over the dressing. Place a crouton on top of the dressing. Repeat the above process with the remaining ingredients. Use four slices of tomatoes and 3 croutons for each salad. Garnish with parsley and serve.