When in doubt how to use leftover cauliflower, try it this way:
Rub it through a sieve, white sauce and all. Have milk on the stove to boil exactly as if for oyster soup.
When it has boiled up, add the cauliflower and let come to a boll and serve at once.
If I have a sufficient quantity of peas left over, utilize them in the same way, and they are always relished.