Bring a large pan or stockpot of water to the boil, remove the ends of the stems, rinse the cauliflowers, and add to the boiling water. You can keep the leaves intact - they're delicious!
Bring back to the boil, then reduce the heat, and simmer for 10-15 mins, until softened but still offer a bit of resistance when inserting a knife.
Once the cauliflowers are cooked, remove them from the pan, and place into a suitably-sized oven dish or roasting pan.
While the cauliflower is cooking, make a roux by melting the vegan margarine in a medium heavy-based pan over a low-med heat. Once the margarine has melted, stir in the flour to make a paste (roux).
Cook the roux for 2 mins, while stirring continually.
Whisk in a little of the milk, to loosen the roux, then whisk in the rest, a little at a time, until all the milk has been added, and there are no lumps.
Whisk in mustard and miso, and continue to cook - stirring all the time - until the sauce has thickened to a custard-like consistency.
Turn off the heat, and add the cheese and nutritional yeast. If using my extra mature cheddar, you should be able to just break it up and whisk it in (or use a blender). If using grated store-bought cheese, stir it in. Keep stirring, until the cheese has melted, and the sauce is smooth.
Stir in the white pepper and the cream.
Pour the cheese sauce over the cauliflowers, making sure they're well-covered, then place into the centre of the oven for around 15 minutes, until the sauce has browned and started to bubble.
When done, remove from the oven, sprinkle with some smoked paprika, and serve immediately.
Leftovers can be kept for a couple of days in the 'fridge in a covered dish. Cauliflower cheese does not freeze well.