Bring a large saucepan of water to a boil. Add the cilantro, making sure to push all the leaves under the boiling water. Blanch the cilantro for 5 seconds. Drain and immediately plunge into a bowl of ice water. Drain well and squeeze out all liquid.
In a blender, puree the cilantro with the olive oil. Strain the puree through 6 layers of cheesecloth or a paper coffee filter and put in a sterilized glass bottle, tightly capped.
Store in the refrigerator for up to 2 weeks.
c.1996, M.S. Milliken & S. Feniger, all rights reserved