Add oil to a large Dutch oven set over medium heat. Add onions, stir; cook, stirring frequently, until onions have caramelized, de-glazing pan with small amounts of water as necessary, about 45 minutes. Increase heat to medium-high; add wine and cook until liquid is reduced by half, about 10 minutes. Increase heat to high. Add stock, bay leaves, thyme, worcestershire, and Creole seasoning. Bring to a boil, cover, reduce heat to medium-low and cook until onions break down and soup is thick, about 2 hours. 

Heat a low broiler.

For each serving fill an individual oven-proof soup crock with hot soup; top with toasted bread rounds, top bread rounds with cheese. Broil until cheese is melted and golden.