'Tis the season for soups! When the temperatures dive, there is simply nothing that takes the chill off like soup. The wonderful thing about soups is their enormous variety: they can be thick and stick-to-the-ribs, whole meals in themselves, or they can be light, even austere, just enough to whet the palate as the start of a formal meal or as a light supper.
Here is a lovely example of a medium-bodied soup, none too heavy but very satisfying at the same time. It's particularly nice during the holiday season, when you may feel like something warming but not too filling, a nice respite between those humongous holiday meals. The starring role is played by the leek, an often overlooked member of the onion family. Or, at least, I tend to overlook it, which is too bad because it has an incomparably savory yet mellow taste that makes any dish that contains it truly special.
Ingredients (for 4-6 servings)
5 leeks
100g (4 Tbs.) butter, or a combination of equal parts butter and olive oil, or just olive oil
20g (2 Tbs.) flour
Salt and pepper to taste
1 liter (4 cups) broth
4-6 slices of good-quality crusty bread
Grated parmesan or gruyère cheese
Directions
Rinse the leeks if necessary (see below) and trim off the root end and green tops. Cut the stalks into thin slices.
Sauté the leek slices in the butter, butter and oil mixture or the oil over gentle heat until they are well reduced and quite tender, without browning, about 15-20 minutes. Season the leeks with salt and pepper just after you add them to the skillet.
Sprinkle the flour and mix it in well, letting it sauté as well for a minute or two. Then add the broth, mix it well to fully incorporate the flour into the liquid, and let simmer, semi-covered, for another 15-20 minutes.
Meanwhile, toast your slices of bread and place each slice in the bottom of a soup bowl for each diner. Sprinkle the slices with some grated cheese. When the soup is done simmering, ladle over a nice serving into the soup bowls. Sprinkle over some more cheese and top with a nice grinding of black pepper and—if you like—a drizzle of best quality olive oil.
You can serve this soup immediately, but it is best after a few minutes' rest, which allows the soup to soak into the bread.
NOTES: These days leeks are often sold pre-washed, and can be used without fuss. But if you see that your leeks are gritty, make sure to wash them well before using. You will need to split them down the middle to make sure you remove all the grit. And, by the way, don't throw away the green tops—they are a great addition when making homemade broth, either instead of or in addition to the onion.
Speaking of which, for a simple soup like this one, where success or failure will depend on the quality of the ingredients, the broth should really be homemade. (See this post for the master recipe.) You can make your broth with beef (the usual choice) or chicken or a mixture of the two—the so-called brodo classico—and, this time of year, you can also use a turkey carcass if you happen to have one around the house…If you want to go vegetarian, then vegetable broth will, of course, do the job.
The choice of sautéing medium will subtly influence the dish. The traditional recipe calls for all butter, which gives the recipe a pleasant sweetness. But, personally, I prefer to use olive oil or a mixture of butter and olive oil, which provides a more 'rustic' taste. Some recipes add potato to the soup, which gives it more body. You can pass the soup through a food mill for a smoother texture. And instead of the toasted bread, you can fry up some croutons in olive oil, which again makes the soup a bit richer.
If you want to get fancy, you can gratinée this soup in terracotta soup bowls as you would a French onion soup, placing the bread on top of the soup, then sprinkling over all the cheese (use gruyere for this variation), drizzle with some olive oil (or melted butter) and run the soup under the broiler or in a very hot oven for a few minutes, until the top is nicely browned.
