Add basil, walnuts, garlic, parmesan, salt and pepper to a blender or food processor.
Slowly drizzle in the olive oil as you blend the other ingredients.
Store in a container with an airtight lid, or follow the tips below to freeze your pesto.
Notes
Add a few mint sprigs or a squeeze of lemon juice for an extra layer of bright flavor.
To keep your basil fresh, trim the stems and place in a jar or vase filled with water (much like you would for fresh flowers).
Cover the container loosely with a plastic grocery bag and store in the refrigerator to preserve freshness.
Frozen pesto keeps well for up to six months. Defrost the cubes in your fridge overnight, or stir the cubes directly into hot pasta for the easiest sauce.