Combine avocado and Greek yogurt in the bowl of a food processor. Process for 1 minute until smooth and creamy, scraping down the sides of the bowl half way through.
Add remaining ingredients and process again for 2 minutes until very smooth and only tiny bits of the cilantro are visible.
Transfer to a serving bowl or place in an airtight container for storing. Can be stored int the refrigerator for 1-2 days. It will not lose it's vibrant green color.
If you like the sauce a bit thinner add more half and half, just a little at a time and stir well till it's the right consistency.