Onion soup is one of those soups that most people like. I have served it as a soup of the day in many restaurants and have found it to be a good seller, and while there are as many different variation as there are chefs, I like a nice roasted onion soup the best. And the good news is that it's easy to make.
I like to use a variety of onions to make this soup. Here I have red onion, white onion, yellow onion shallot and garlic. The ratio of the mix isn't that important really, just as long as the majority isn't garlic. If it was, you would be making roasted garlic soup - which is fine - but it isn't what I have set out to do here, so keep that in mind!
Toss the mixed onions in a bit of olive oil and roast them in a pan in the oven at 375 degrees until golden brown.
Place the roasted onions in a sauce pot, add some chicken stock, sliced potato, thyme, white wine, white wine vinegar sugar and salt. Bring to a simmer and cook until potatoes are soft.
Return soup to the pot and bring back to a simmer. Season with salt, pepper and sherry to taste. Add a little more vinegar if desired also.