I've tried a couple low-carb zuppa toscana recipes and I love this one: http://www.camacdonald.com/lc/Cookbook/0801.html

As you can see, it calls for mashing the cauliflower with cream cheese which really thickens the soup nicely.

Here's the nutrition info I have for it in My P.L.A.N. (Note: I used breakfast sausage because it was much lower in carbs than the Italian sausage I looked at. If you can find good Italian sausage with no crappy fillers, use it.)