Dice raw bacon into 1/2" pieces. In chafing dish or skillet, saute bacon until lightly browned. (Vegetarian version: put oil in skillet and heat.) Add vinegar, Worcestershire sauce, lemon juice, and sugar, stirring until sugar is dissolved. At the table, add cognac or brandy and quickly ignite. Stir gently and while still flaming, ladel over individual mounds of spinach on salad plates. Serves 6.