1. Heat the oven to 180degC (fan) / 200degC (standard)
2. Cut the cauliflower into florets, and the main stem into chunks. Also chop the leaves. The leaves add colour and additional nutrition. Place these in a baking dish and dry-bake in the oven while preparing the saurce. A little charring adds to the flavour.
3. Now make the bechamel sauce. Coarsely chop the onion and gently fry in oil until soft. Add a pinch of salt and a little turmeric and/or chilli if desired.
4. Add the butter beans including liquid and bring to a low simmer.
5. Using a stick blender, blitz until smooth.
6. Grate the cheddar / vegan cheese and stir into the smooth sauce while heating, letting the cheese melt.
7. Remove the cauliflower from the oven,  pour over the sauce, then return to the oven for about 20 minutes or until little browned, rotating the dish once to keep the browning even.
8. Remove from the oven and let stand for 2-3 minutes before serving.

The dish can be enhanced by adding a tin of well drained kidney beans to the cauliflower (so they remain whole).