Classic French Onion Soup

I was eighteen the first time I ate real French onion soup, at a small bistro in Paris where I had wandered in alone on my first trip abroad. I ordered the soup because it was cheap and I was nervous about my limited French. The waiter brought out a heavy ceramic crock with a thick crust of bubbling, golden cheese covering the top — almost like a lid. I broke through the cheese with my spoon and the smell that came out is something I can still describe twenty years later. Deeply caramelized, almost beefy, with a slight sweetness and a sharp note from the wine. I ate the entire bowl, ordered a second piece of bread to mop up every last drop, and decided that I needed to know how to make this soup at home.

The answer, as it turns out, is mostly about the onions. You have to caramelize them properly — and properly means much longer than you think. The first time I tried, I thought I was done after twenty minutes. Wrong. The onions need a full 45 minutes to an hour of slow, low-heat cooking, stirring every few minutes, until they have collapsed into a sticky, glossy, deep mahogany mass. They reduce by about 80%. They lose all their crunchy bite. They become almost jam-like. This is the foundation of the soup, and there is no shortcut. Anyone who tells you otherwise has never made truly excellent French onion soup.

The second key is the broth. Use the best beef broth you can find or make. If you make your own from beef bones, even better — the gelatin gives the finished soup a glossy, almost luxurious body. If you are using store-bought, look for low-sodium, high-quality broth and supplement with a splash of beef bouillon paste or Worcestershire sauce for depth.

The third element is the wine. A dry white wine — something like a Sauvignon Blanc — deglazes the pan beautifully and brings a sharp brightness that balances the deep sweetness of the caramelized onions. Some recipes call for brandy or sherry, and a small splash of either at the end adds extra dimension. I always finish my soup with about a tablespoon of brandy stirred in just before serving. It is the kind of touch that makes people lean forward and ask 'what is in this?'

The finishing move is the broiler. You ladle the soup into heatproof crocks, top each with a slice of toasted baguette, pile on a generous handful of grated gruyere, and run them under a hot broiler for two or three minutes until the cheese is bubbling, browning at the edges, and pulling away from the sides of the crock in golden waves. The cheese on a properly broiled French onion soup is the entire point. Do not skimp on it.