Cut the hard core and stalks from the cauliflower and pulse the rest in a food processor (chopping up finely with a knife works as well, or even the grater to make grains the size of rice. Tip into a heatproof bowl, cover with cling film, then pierce and microwave for 7 mins on high – there is no need to add any water. Stir in the coriander. For spicier rice, add some toasted cumin seeds.