Place a heavy based casserole pot over a medium heat
Add the butter and allow to melt.
When its melted, add the sliced onions and stir well so the onions are coated by the butter.
Reduce the heat to low and allow the onions to gently cook for 25 - 30 minutes until the onions have softened and translucent.
Increase the heat back to medium. Add the salt, stir well.
Cook for a further 20 minutes until the onions are golden brown.
Add the wine and stir well deglazing the bottom of the pot for a couple of minutes. Most of the wine will evaporated but the goodness stuck to the bottom of the pot will be released.
Add the flour over the onions, stir and cook for a minute.
Add the broth/stock and the fresh thyme and stir well.
Cover the pot and reduce the heat to a simmer for 25 - 30 minutes.
Whilst the soup is simmering away,
Preheat the grill
Grate enough cheese for your liking. I like a lot.
Put your bread into a toaster and toast.
Remove from the toaster, butter(optional) a little and top with the grated cheese.
Place the cheesy toast under the grill until the cheese has melted thoroughly.
Slice the toast into manageable pieces.
Ladle the soup into warmed bowls and add the cheesy toast on top.