Fill and boil your kettle. Tip the lentils into a bowl, cover with cold water and soak for 10 mins. Peel and finely chop the onion. Pull the leaves off the cauliflower and set it to one side. Wash and finely chop the leaves. Set a large pan on a low heat. Add 1 tbsp oil, the onion and the cauliflower leaves. Fry for 5-6 mins, stirring now and then, till soft.
Meanwhile, peel and grate the ginger and garlic. Halve the chilli, flick out the seeds, and finely chop it. Add the ginger, garlic and chilli to the pan. Fry for 1 min, then stir in 1 tsp turmeric.
Drain and stir in the lentils. Pour in 800ml boiling water and add a pinch of salt. Stir, cover and simmer for 15 mins till the soup has thickened.
Halve the pomegranate. Hold 1 half, cut-side down, over a bowl. Hit the back with a wooden spoon and the seeds should fall into the bowl. Repeat with the remaining half. Roughly chop the coriander stalks and leaves.
Finely chop the cauliflower florets and stalks. Set a large frying pan on a medium heat. Add 1 tbsp oil, the cauliflower and some salt. Fry for 5 mins, stirring, till browned and a little tender. Add 2 tsp black mustard seeds and 1 tsp cumin seeds. Stir and fry for 2 mins till aromatic. Take off the heat.
Stir half the cauliflower and coriander into the soup. Blitz smooth, or leave the soup chunky. You can add more hot water if it’s too thick, and a pinch more salt if needed. Ladle the soup into 2 bowls. Top with the cauliflower, pomegranate seeds and the remaining coriander to serve.