Slow Soupers~ French style

The slow souper's soup of the week is offered by Sharon from California. She says the secret of this delicious soup is to caramelize the onions before adding the broth... adding an extra layer of flavor~ much like a good roux.
French Onion Soup
2 lbs. yellow onions, peeled, halved lengthwise, then sliced thinly crosswise
2 T oil
2 T butter
3 sprigs fresh thyme
1 dried bay leaf or 2 fresh bay leaves
¾ tsp salt
¼ tsp sugar
2 tsp all-purpose flour
½ tsp freshly ground black pepper
¾ C dry white wine (or red wine)
6 C reduced-sodium beef broth (48 fl oz.)
6 diagonal slices of baguette
½ lb shredded Gruyère (or Comte or Emmental) cheese
2 T finely grated Parmigiano-Reggiano cheese (optional)
Heat butter and oil in a heavy 4- to 5-quart pot. Add onions, thyme, bay leaves, sugar and salt. Stirring frequently, cook onions over moderate heat until they are very soft and deep golden brown, about 45 minutes. Add flour and pepper, and stir for 2 minutes.
Add wine and stir for 2 more minutes. Then add broth and simmer uncovered, stirring occasionally, for 30 minutes.
While soup simmers, preheat oven to 350°F. Arrange bread in 1 layer on a baking sheet and toast, turning over once, until completely dry, about 15 minutes. Remove croutons from oven and preheat broiler. Put heat-proof soup bowls in a shallow baking pan.
Discard bay leaves and thyme from soup and divide soup among bowls, then put a crouton in each. Add enough shredded Gruyère to cover crouton, then sprinkle each with Parmigiano-Reggiano (if using). Broil until cheese is melted and bubbly, 1 to 2 minutes.
If you want to make ahead: Soup can be made and refrigerated or frozen (of course, do not add croutons and cheese to soup if making ahead); cool soup completely, uncovered, then refrigerate for up to 3 days or freeze. Reheat soup before proceeding with recipe. The only change I made was to add 2T of WhistleStop Marinade to the sliced onions a few minutes before cooking. This was awesome!
I made our soup before heading to Boston... It would sure be warm right about now!

Y'all enjoy!
Sandi