In a large, heavy bottomed pot on medium heat, add the butter and olive oil.
Add all of the sliced onions and shallots, along with the sugar, salt and pepper.
Cook slowly, stirring occasionally, until a deep golden brown.
Stir more frequently the closer you get as the sugar content may cause them to turn quickly. You want it to look like this...
Add the wine and vegetable broth and taste for seasoning. Add additional salt and pepper as needed.
Meanwhile, slice the bread and preheat the broiler.
Toast one side until golden and flip, adding the cheese. Broil until golden on top. Add the toast to a bowl of hot soup when ready to serve and garnish with parsley, if desired.