I love cauliflower and this is my ultimate happy dish.  Don't throw the leaves or core away.  Wash the leaves and cook them according to this recipe or put to one side for another day.  The central core is nice cut into batons and put into a stir fry.

Ingredients
1 large cauliflower
175g mature cheddar, grated
75g gruyère grated
75g parmesan (or vegetarian alternative), grated
700ml full-fat milk
50g butter
50g plain flour
1 tsp Dijon mustard
25g breadcrumbs
15g crispy onions or shallots (optional)

Method
Preheat the oven to 190c.

Meanwhile melt the butter in an oven proof saucepan (big enough to take all of the sauce and cauliflower), over a medium high heat and then stir in the flour and cook out for 1 minute, stirring constantly.  Take off the heat and gradually add the milk and continually whisk until smooth.  Put back on the heat and cook for 5 minutes or so, this will make the sauce go beautifully glossy.

Cut the leaves off of your cauliflower, and break or cut off the florets from the central core.  If you have a microwave then clean a plastic carrier bag  (you don't need to dry) and put the cauliflower inside the bag and seal (you want to steam them so seal it well).  Put into the microwave on full power for 5 minutes.

Mix the cheeses together and put to one side.  Turn off the heat and add the mustard and stir again then add three quarters of the cheese stirring until melted.  Check for seasoning and add more salt if needed and ½ tsp of ground white pepper and stir through. 

Put the cauliflower into the cheese sauce and carefully stir to ensure all of the cauliflower is covered.  Mix the remaining cheese with the breadcrumbs and crispy onions if using and scatter over the top.  Put into the oven for 20-30 minutes until bubbling and golden.