Pipe the yogurt or cream into a spiral or concentric circles with a dot in the center on top of your soup. A spiral would probably look more realistic, but I made concentric circles because I found it easier.
Run a toothpick from the center of the circle outwards through the circles to the edge of the bowl. Repeat the process, continuing all the way around the bowl to make an instant spider web!
Use the caramelized onions to form an onion "spider" on top of the creamy web.