Remove the largest stems from cilantro, but leave most of the stems because they are full of flavor. Chop very coarsely.
Peel and seed the avocado. Add the avocado, cilantro and garlic to blender first. Pulse those a few times then add all the other ingredients and blend until smooth.
You can adjust consistency with the heavy cream, if you want to use as a dressing and don't like it thick.