French onion soup is a classic. And yet, it is so easy to find a bowl of unsatisfying French onion soup. Why? Because the soup relies on only a few ingredients for its flavor, so those ingredients have to be done RIGHT.
Warming French Onion Soup
3 sweet onions, thinly sliced
1 T brown sugar
2 1/2 cups good beef stock
1/2 cup dry wine
salt and pepper
2 slices stale French or Italian bread
grated cheese-Gruyere is great, but grated Mozzarella is cheap–your call
Place a cast-iron skillet over medium-low heat and add a little oil. Add the onions and a pinch of salt and stir a few times. Check that the heat is low enough not to immediately brown the onions but high enough to slowly cook them. Walk away. You can come back to stir occasionally, but what you really want is for the onions to turn dark caramel brown throughout without burning. Which requires time–count on an hour. About 5 minutes before you think they’ll be ready, add the brown sugar so that it can add to the caramelizing.
Meanwhile, heat your beef stock. Add it to your onions, add the wine, and season with salt and pepper.
You can do the next step right in your cast iron, but if you have oven-proof single-serve bowls it makes a better presentation. Turn on your broiler. Put the bread on top of the soup and a generous amount of grated cheese on the bread.
Broil just until the cheese is melted and bubbly. Serve immediately.
Recipe notes: It is important to use a sweet onion such as a Vidalia because French onion soup relies heavily on caramelization– and sugar is the component that caramelizes.
I actually didn’t use the stock/wine combo above-I’d braised beef in a wine/stock mix, adding the meat juices to the already rich flavor. This makes the soup a great vehicle for leftover fluids, but you can manage by just using good quality stock.
I would not use extra virgin olive oil in this recipe–the aromatics may burn before the onions are done. You can use clarified butter instead if you prefer.