I used to make the sauce by making a roux but since I've been low carbing I use a dollop of cream, a dollop of cream cheese and grated cheese. It's much nicer and simpler to make. Then steam the cauliflower, put the sauce over and into the oven for 15 mins.
I used to make the cheese sauce myself, but decided that a tub of cheese sauce from Waitrose Tescos does the job just as well. I add a spoonfull of wholegrain mustard and give it a good stir before I pour it over the cauliflower. I sort of give the cauli a bit of a boil ( 5 mins or so) before the cheese goes over and into the oven for 1/2 an hour.
Sometimes I add a few bits of torn up crispy bacon - sometimes a bit of tomato.
I did a good cauli cheese on Friday night - I made a roux and added warm milk, let the sauce thicken and added a good handful of grated cheddar and about half the same amount of Parmesan. I let it all come together and added salt, black pepper and a tiny bit of nutmeg.
I poured the sauce over the cauli which I'd already boiled (lightly) in florets. I had some stale white bread so I whizzed that into quite big breadcrumbs, topped the cauli with more grated cheese and then out the breadcrumbs on top of that. It not in the Rayburn (at the top, so more like the grill really) for about 15 mins. It was yum!
I've also had good results using blended cottage cheese in the sauce, a sort of variation on this recipe (which is prob the best macaroni cheese recipe in the world EVA):
easier method than a roux is to put milk, flour and marg in pan and whisk a bit as it heats. then add grated cheese and whisk a bit. you can probably get away with 10 whisks in total if you are lazy like me