Makes 1 1/3 cups
For soft herbs, such as basil, parsley, cilantro or tarragon: Use 4 cups packed leaves to 2 cups pure olive oil.
For woody herbs, such as rosemary, sage, thyme, oregano or lemon verbena: Use 1 cup packed leaves to 2 cups pure olive oil.
In a blender, puree the herbs and oil until completely smooth. Put the mixture in a saucepan and bring it to a simmer over moderate heat. Simmer for 45 seconds, then pour through a fine-mesh strainer into a bowl. Don’t press on the mixture, but you can tap the strainer against your hand to get the oil to drip through faster.
Note: Fresh herb oils are better to toss into pasta at the end rather than cook with, so the oil keeps its fresh, uncooked taste.
From Smitten Kitchen http://smittenkitchen.com/blog/2008/06/zucchini-strand-spaghetti/