Green is the color of spring - and to celebrate the beautiful green vegetables that epitomize the season, we've combined baby fava beans, fresh English peas, and tender asparagus in a light and healthful pasta dish that's sure to please. Whole wheat, whole grain spaghetti is our pasta of choice; it's much more nutritious than pasta made from white flour. Look for thin whole wheat spaghetti, such as the Hodgson Mill brand, so the dish stays light and lets the glorious green vegetables shine.
Bring a small pan of salted water to a boil over high heat. Blanch the peas for 30 seconds. Drain, then plunge the peas into a bowl of ice water to cool, and drain again. Set aside.
Repeat the blanching process with the asparagus spears, cooking them for 60 seconds. Set aside.
Bring a large pan of water to a boil, add salt, and then cook the pasta according to package directions.
Meanwhile, heat the oil in a large skillet. When the oil is hot, add the leeks and red pepper flakes. Cook over medium-low heat, stirring frequently, until the leeks are soft, about 5 minutes, taking care not to let the leeks color.
Add the garlic and cook, stirring frequently, for 2 minutes.
Add the wine to the skillet and raise the heat to medium-high. Cook until the wine is absorbed, then add 1/2 cup of hot chicken stock, the lemon zest, and tarragon.
By this time the pasta should be cooked. Drain the spaghetti or transfer the pasta with tongs to the skillet. Cook the mixture, stirring constantly, until the pasta is coated with the sauce. If the pasta seems dry, add another 1/4 cup of chicken stock to the skillet. Stir in the butter (if using), the reserved peas, asparagus, and fava beans, and cook until heated through, 1 to 2 minutes, adding the remainder of the chicken stock if needed. Season to taste with salt and freshly ground pepper.
Divide the pasta among shallow heated bowls and garnish each serving with a sprinkling of cheese. Serve hot.