I don't often make cauliflower cheese in case of yet another addiction to a "dangerous" food.
I use best quality ingredients I can find. Cook the Cauli in florets, briefly. Melt butter in pan, make excellent white sauce with plain flour and full cream milk (ok, I use skimmed but full cream delicious) add lots of best quality cheese. None of that fat reduced stuff - add some powder mustard or if you prefer, as I do, dijon. Pour sauce over cauli, add even more shocking full fat cheese, pop dish under grill.
In my youth, I'd fry bacon to go with the cauli cheese. My concession to being good with this dish, is I leave out the bacon.