Recipe notes by Raymond Blanc
Although onion soups date back to Roman times, this particular soup began life in eighteenth-century Paris as a beef broth with caramelised onions on top.
Now served without the beef, the quality of the onions is crucial. You want both high acidity and high sugar levels to create a fully-flavoured soup.
The best onions are Rose de Roscoff. Spanish onions, although lacking in acidity, will also work.
I like to float croutons on mine and I grate some two-year-old Comté cheese on the top. And make sure you caramelise your onions to achieve a rich, brown colour.
A Frenchman’s heaven!
If you like a strong onion flavour, caramelise the onions for a further 15 minutes, until very dark brown.
By quickly boiling the wine you are removing most of the alcohol, which has a bitterness, but keeping all the fruity qualities and acidity of the wine.
You could replace the water with a brown chicken stock for a richer soup.