Defrost the box of frozen spinach.
SQUEEZE every bit of liquid out of the spinach. You want it to feel SUPER DRY!
In the food processor bowl, COMBINE the dry vegetable soup with the mayo, plain Greek yogurt, spinach, water chestnuts and green onion.
PULSE until everything is well combined. STOP the food processor occasionally to scrape down the sides.
Let the food processor RUN for a minute or so until everything in well combined and evenly chopped.
You want the spinach to be teeny-tiny.
Refrigerate for at least 2 hours before serving with crackers, crostini or fresh veggies.