1 cup shelled fresh English peas
12 asparagus spears (peeled if thick, cut on the diagonal into 2-inch lengths)
12 ounces whole wheat thin spaghetti (such as Hodgson Mill brand)
2 tablespoons olive oil
2 medium leeks (cut in half lengthwise, then thinly sliced crosswise, white and light green parts only)
  pinch red pepper flakes (or to taste)
4 cloves garlic (minced)
1/3 cup white wine
1 cup chicken stock (hot)
  grated zest of 1 lemon
1 1/2 tablespoons minced fresh tarragon
1 cup shelled, peeled baby fava beans
2 tablespoons butter (optional)
  Freshly ground black pepper
1/4 cup grated Parmigiano Reggiano cheese