I actually wrote the recipe. I think it would be fine if you wanted to add some cauliflower to it to bulk it out, but I'd also increase the amount of liquid. To be honest it might be a bit tricky to get it right.
Say you added half a head of cauliflower to the mix, I'd increase the liquid content by 1/2 a cup at least - a bit more stock and a bit more cream.
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