First start boiling the macaroni.
Then make a white sauce - I find it easiest in the microwave.
Melt a little butter in a bowl (maybe 1 tablespoon, depending on how much of the stuff you're making).
Then mix in about 1-2 tablespoons plain white flour, so that you have a stiff buttery dough.
Now, using a whisk, slowly mix in some milk, whisking it until it's smooth and creamy.
Put that in the microwave for about 33 seconds.
Take it out and whisk quickly before it sets hard.
Now add a little more milk and repeat the process.
At some point, maybe after the 3rd or 4th time, you'll find the mix changing consistency, as the flour starts cooking. If you're making a lot, it'll take maybe 5 or 6 bursts of cooking but if it's only for 1 person it should be done by the 3rd burst.
Add salt and pepper to your taste - little or lots.
That's when you add a heap of grated cheese - lots, if you're a cheese fan. Give that another 40-50 seconds in the microwave.
Some people might find it easier to do this sauce on the stove. My Mum always did but I don't.
The macaroni should be done by now so strain the water off and add it to the sauce (or vice versa - it doesn't matter).
You can eat it at that point but if you want the crunchy topping you'll need to put it in an oven-proof dish and sprinkle more grated cheese in top.
Then put it in the oven - or under the grill until the colour and aroma tell you it's done.

That's the way I make cauliflower cheese too - and that sauce goes well with spaghetti squash as well.

Robyn