Pesto is a versatile Italian sauce made of basil, garlic, pine nuts, salt and grated Parmesan cheese. Making pesto doesn't require any cooking, but if you're planning to freeze it, cook the basil briefly in salted water beforehand to preserve its vibrant green color. Also, if you're planning to freeze the pesto, omit the grated Parmesan cheese; if you'd like, you can add the cheese once it's defrosted, though it's not necessary. Freeze the pesto first in an ice cube tray, then transfer the cubes to a resealable plastic bag for easy access to small batches.
Defrost cubes (2 tbsp.) of frozen pesto at room temperature for about 20 minutes. Once thawed, mix the pesto with a fork. Add 1/2 tsp. of grated Parmesan cheese and mix well.
Defrost pesto cubes overnight in the refrigerator. Once thawed, mix up the cubes with a fork. Add 1/2 tsp. of Parmesan cheese per 2 tbsp. of pesto and stir well.
Defrost frozen pesto in the microwave at medium heat, mixing it every 30 seconds. Be careful not to overheat the pesto; you don't want it to cook and lose its fresh taste.