Cauliflower cheese is the ultimate side dish, and I’ve used four cheeses because they all bring different qualities in this gratin. The English mustard and truffle oil give it a good boost of flavour.
125g ball mozzarella, torn into pieces
200g gruyère or cheddar, grated
30g crispy onions
For the sauce
25g plain flour
300ml whole milk
30g English mustard
100g cream cheese
1 tsp truffle oil (optional)
100g parmesan or vegetarian alternative, finely grated
For the sauce, melt the butter in a shallow saucepan. When it’s just starting to sizzle, stir in the flour to make a paste. Cook for a minute, then gradually whisk in the milk until you have a smooth, thick sauce. Stir through the mustard, cream cheese, truffle oil (if using) and parmesan, and cook over a low heat until thickened. Season with lots of black pepper.
Heat oven to 140C/120C fan/gas 1. Trim the leaves off the cauliflower and slice into rough steaks about 1cm thick. Don’t worry about the outside bits not being slices – it will all be used. Assemble the dish a bit like a lasagne. Spoon a quarter of the cheese sauce into a large baking dish and spread it out, then add half of the cauliflower. Repeat the process, finishing with a thick layer of sauce. Scatter over the mozzarella, and the gruyère or cheddar and crispy onions
Bake for 1 hr 30-1 hr 45 mins until the cheese is golden and the cauliflower is soft but not mushy. If you want a golden finish, you can grill it (keep an eye on it) or leave it in when you turn the oven up for the crackling. Once baked, leave to stand for 10 mins before serving in the middle of the table.