serves: About 4 cups of sauce, enough for 1 pound of pasta
Here's a fitting sauce for springtime, full of seasonal treasures: asparagus, sweet peas, scallions, leeks and fresh mint. And the color? Springtime green! Of course, since all of the ingredients are available year round, you can enjoy this anytime. But it is truly splendid when made with produce in season. Fresh asparagus—locally grown if you can get it—is the foundation of this sauce, both its sweet flavor and the pleasing texture of finely sliced vegetables. Use skinny asparagus spears for uniform appearance and easy slicing (and don’t throw away the stubs, see recipe that follows). If available, fresh sweet peas are wonderful in the sauce. If not, frozen peas are always acceptable.
1½ pounds asparagus, preferably 1/2-inch wide or less
6 tablespoons extra-virgin olive oil
1 medium onion, finely chopped
1 large leek, green and white parts, sliced into 1/2-inch pieces
1 teaspoon salt
½ teaspoon peperoncino, or to taste
10 ounces frozen peas, thawed or 1 pound fresh peas
2 cups scallion, finely chopped
2 tablespoons butter, cut up
⅓ cup water, plus more if needed
½ teaspoon fresh mint, shredded
Rinse the asparagus, snap off the tough bottom stub of each spear (and save, see the recipes that follows). Slice each spear crosswise in 1/4-inch pieces—if the spear is fatter than 1/2-inch, slice it lengthwise in half or quarters. You want the asparagus pieces to be approximately pea-size. Slice the spears to make 4 cupfuls.
Pour 1/4 of the oil into the skillet, set over medium-high heat and stir in the onions. After a minute or 2, when the onions are gently sizzling, stir in the leek pieces and 1/2 teaspoon of the salt. Cook for a minute, drop the peperoncino into a hot spot to toast briefly, then stir and cook until the leeks are hot and starting to wilt, 3 minutes or so.
Dump in the green peas and stir with the other vegetables. Cover the pan, lower the heat, and let the vegetables cook, sizzling gently. Shake the pan frequently, uncover it occasionally, and adjust the heat as needed to make sure the onions aren't in danger of burning.
After 6 minutes or more, when the onions are pale gold and the peas are softening, stir in the asparagus pieces and the scallions, then the butter and another 1/2 teaspoon salt. Pour in 1/3 cup of water and stir well to moisten everything.
Bring the sauce to a slow simmer and keep it cooking, very slowly, over low heat, for about 30 minutes. Stir occasionally and add spoonfuls of water to the sauce if it seems to be getting dry. The vegetables should become very soft but still retain their shape and identity—the sauce as a whole should be moist and thick. When it's reached this stage, turn off the heat, and stir in the 2 remaining tablespoons of olive oil and the shredded mint leaves.
Use right away or let it cool. The sauce can be refrigerated for several days. If frozen, the texture will change but the flavor will be fine—it will keep for several weeks.