On medium heat, add your onions to melted butter.

Stir occasionally. You want the onions to caramelize which will take 30-45 min. Lower your heat if they brown too quickly

Add wine and sherry and allow the alcohol to cool off for a few minutes

Add the flour and stir for a couple of minutes until flour is a nice golden brown color

Add broth and bring up to a boil.

Allow to simmer on low heat until your ready to serve it.

Cut bread into 1/2-3/4” slices and toast

In oven safe dish, add soup and then a slice of toasted bread and a healthy layer of cheese

Pop into broiler for a few minutes. Once the cheese starts bubbling, take it out