To a dutch oven, or deep soup pot, add butter and melt on medium heat
Add sliced onions and stir frequently for 15 minutes until color starts to darken
After 15 minutes add brown sugar, garlic, Worcestershire, bay leaf, thyme and salt to taste
Continue to stir for another 15 minutes or until color has deepened further
Deglaze with white wine and cover for 1 minute
Add flour and stir for another minute
Add beef broth and cover for 20-30 minutes and simmer on medium low
Fish out thyme and bay leaf before serving
To finish dish add croutons and cheese on top of soup in individual oven safe bowls, broil on high for 2 minutes or until cheese crust is melted & bubbling
For croutons
Slice baguette into crouton shape by dicing the bread slices
Drizzle with olive oil liberally and season with kosher salt
Roast croutons at 425 for 5-7 minutes or until crunchy and golden brown