Preheat the oven to 180°C/350°F/gas mark 4. Reserve one floret of cauliflower and steam or boil the rest until soft. Chop up the cooked cauliflower as finely as possible and put it into a bowl with the curd cheese. Add the eggs and egg yolks and whisk together thoroughly. Then stir in the mustard and season with salt and black pepper. Pour the mixture into a buttered 23 cm/9 in round ovenproof dish and cook in the centre of the oven for 20-25 minutes, just until set.
When the flan is ready, remove from the oven and turn the heat up to 240°C/475°F/gas mark 9. Slice the reserved cauliflower floret lengthways as thinly as possible and arrange the slices in a circle on top of the flan. Sprinkle with the grated cheese. Put the flan back on the top shelf of the oven for 8-10 minutes, until the cheese is speckled brown.