Fry the onions in the knob of butter on a medium high heat

Allow the onions to catch slightly on the bottom of the pan and caramelise slightly before stirring and allowing more of the onions to caramelise.

Do this for about 10 minutes until all the onions are a golden brown.

You can carry on cooking for another 5 minutes without sugar or add the sugar which will help caramelise the onions to a darker colour which makes for a richer, more  flavorsome soup.

Add the brandy and stock and oregano and simmer on a medium heat for 10 more minutes.

Add salt and pepper to taste.

Whilst the soup is the final stages of simmering, slice the bread, top with the grated cheese and grill until golden.

Serve the soup into bowls and top with the cheesy crouton.