Pesto freezes very well, but if you plan on freezing it, omit the cheese and add it only when you are ready to use the pesto. For the purposes of developing this recipe, I used a kitchen scale, which is a more accurate and practical way to measure most ingredients, especially leafy vegetables. However, depending on how much pesto you want to make, use my ingredient measurements as a guideline depending on the quantity of spinach, basil, and parsley you are using.
- 3 ounces (86 grams) basil leaves
- 1 ounce (26 grams) Italian flat-leaf parsley leaves
- 5 ounces (142 grams) pre-washed baby spinach
- 2 garlic cloves, peeled and trimmed of tough ends
- Zest and juice of 1 large lemon
- ½ cup (76 grams) pine nuts
- ¾ teaspoon salt
- ¾ cup (177 mL) extra-virgin olive oil (plus more if necessary)
- Pecorino Romano or Parmigiano Reggiano (How much you use will depend on the amount of pesto sauce you are using. Mix the cheese in ¼ cup at a time and taste as you incorporate it to make sure you are not over-salting the pesto sauce.)
- Remove the basil and parsley leaves from the stems and wash them in cold water. Spin the leaves dry in a salad spinner and lay them on a clean dish towel to air-dry for about 20 minutes. Blot away any remaining moisture using paper towels. Set aside.
- Place the baby spinach in the bowl of a food processor fitted with the steel blade. Pulse a few times to coarsely chop the spinach. Next, add in the basil and parsley leaves and pulse a few times to chop and incorporate them into the spinach. Add in the garlic cloves, lemon zest, lemon juice, pine nuts and salt, and pulse to incorporate them into the greens. With the machine running, pour the olive oil through the feed tube in a thin stream until the pesto is smooth and thick in consistency (it should not be runny). Scrape down the sides of the bowl to ensure all the ingredients are evenly incorporated and run the machine again to properly emulsify the oil into the other ingredients.
- If you will be using the pesto immediately: Transfer the amount of pesto you want to use into a serving bowl large enough to accommodate the amount of pasta you are making and stir in the cheese. As the pasta finishes cooking, ladle out about ½ cup of the hot pasta water into a heat-proof measuring cup and set it aside. Drain the pasta through a colander, add it to the serving bowl, and toss to coat the pasta evenly with the pesto. If the sauce seems too thick, dribble in small amounts of the pasta cooking water to thin the sauce gradually. It should take on a creamy consistency and cling to the pasta evenly.
- Storage: If you will not be using the pesto right away, transfer it into freezer-safe containers and smooth the top surface with a spatula. Cover the surface of the pesto completely with a thin layer of olive oil and close the container tightly. Refrigerate and use within 3 days, or freeze for up to 3 months. You can also transfer the pesto sauce into an ice cube tray if you want to have smaller portions. Once the pesto cubes have solidified, pop them out and transfer them into a freezer-safe zip bag and return to the freezer.