- Preheat the oven to 200°C/Fan 180°C/Gas 6. Bring a large pan of salted water to the boil, add the cauliflower florets and cook for 4-5 minutes until just tender. Drain and refresh in iced water, drain again and transfer to a large ovenproof dish.
- To make the sauce, melt the butter gently in a clean saucepan then stir in the flour and mustard powder over a low heat to make a roux. Once the butter and flour comes together as a smooth paste, gradually start to add the milk a little at a time, whisking continuously until completely smooth and all the milk has been added.
- Bring to the boil and simmer for a few minutes, stirring continuously, until the sauce thickens so that it coats the back of the spoon. Remove from the heat and mix in the cayenne pepper along with seasoning to taste.
- Mix together the three cheeses in a large bowl. Add half to the pan and stir until fully melted into the hot sauce. Pour the cheese sauce all over the cauliflower in the dish.
- Add the breadcrumbs and thyme leaves to the remaining cheese and mix together in the bowl to create a cheesy crumble. Sprinkle this all over the dish, covering the cauliflower and sauce completely.
- Transfer to the preheated oven and bake for 15-20 minutes until the topping is crisp and golden and the sauce is bubbling.
Tips: We’ve used a combination of three British cheeses for maximum flavour in our cauliflower cheeses sauce, but you could use all Cheddar or a combination of other hard cheeses as you like.