====== Ingredients ======
  * 3 to 5 cloves garlic
  * 1 cup pine nuts, slivered almonds or walnut halves
  * 2 tablespoons grated Parmigiano-Reggiano cheese, or to taste (optional)
  * 1 teaspoon freshly ground black pepper
  * 1/2 teaspoon fine sea salt
  * 4 packed cups chopped fresh basil leaves
  * 1/2 cup extra-virgin olive oil, plus more for storage
  * Juice of 2 lemons
  * Crushed red pepper flakes to taste (optional)

====== Preparation ======

  - Put the garlic in the bowl of a food processor and pulse until coarsely chopped.
  - Toss in the nuts, Parmesan, if using, pepper and salt and chop until the nuts are finely crushed, about 1 minute.
  - Add the basil, oil and lemon juice and pulse for 1 minute more, until smooth.
  - Stir in red pepper flakes, if desired.

To store, transfer the pesto to a sterilized jar with a tight-fitting
lid.
Pour a thin layer of olive oil on top of the pesto, seal and
refrigerate up to 10 days or freeze up to 3 months.