Finely dice the chard stalks and throw them into a large saucepan with the onion, tomatoes and 3 tablespoons water. Cook gently for 10 minutes, until starting to soften. Add a dash more water if they look like catching.
Add the lentils, garlic, ginger, chili and spices. Cook for 2 more minutes before adding the butter beans and stock. Season lightly with salt and pepper and bring to a gentle simmer. Cook for 25–30 minutes, stirring frequently, until the lentils are completely soft. Top up with a dash of extra water if it looks too thick.
Meanwhile, warm the olive oil or a tablespoon water in a large non-stick frying pan. Fry the cauliflower over a medium heat for 2–3 minutes on each side, until golden brown. Add to the dhal along with the mustard for the final 10 minutes of cooking time.
When ready, finely shred the chard leaves and stir them into the dhal until wilted; this will take only a couple of minutes. Finish with a good squeeze of lemon juice. Taste and adjust the seasoning to your liking.
Serve the dhal alongside rice or flatbreads and garnish with the fresh coriander.