Leeks are onions’ milder cousins, and when they cook down they become sweet and creamy. Red onions add depth of flavor, making this a perfect pasta sauce for when the weather starts turning cold.
1 medium red onion
4tablespoonsextra-virgin olive oil
2 medium leeks
Freshly ground black pepper
6–7sprigsflat-leaf Italian parsley
1poundfusilli (spaghetti is also good)
½cup freshly grated Parmigiano-Reggiano
Fill a pot for the pasta with about 6 quarts of water, place over high heat, and bring to a boil.
Peel and thinly slice the red onion crosswise. Put it with the olive oil in a 12-inch skillet and place over medium-high heat. Sauté the onion while you are preparing the leeks. If the onion begins to brown, remove from the heat.
While the onion is sautéing, cut off the root ends of the leeks and trim the tough dark-green tops of the leaves. Cut the leeks into narrow strips 2 to 3 inches long, put them in a bowl, and cover with water. Swish the leeks with your hands to remove any dirt. Lift the leeks out of the water in the bowl and add them to the pan. Season with salt and pepper and add about ½ cup of water. Cover the pan, lower the heat to medium, and cook until the leeks are very tender, about 15 minutes. Check them periodically and add more water if the liquid evaporates before they are done.
While the leeks are cooking, finely chop enough parsley to measure about 2 tablespoons.
After the leeks have cooked for 15 minutes, add about 2 tablespoons salt to the boiling pasta water, add the fusilli, and stir well. Cook until al dente.
When the leeks are done, uncover the pan, and if there is still liquid in the pan, raise the heat until the liquid is almost completely evaporated. If the pan is completely dry, add about ¼ cup of the pasta water to moisten. Stir in the parsley and cook for another minute.
When the pasta is ready, drain well, toss with the sauce and the grated Parmigiano-Reggiano, and serve at once.