Melt the butter in a saucepan and put in the onions and garlic, then fry for 5 minutes until they turn golden. Add the curry powder and tomatoes and cook over a high heat for 5 minutes until the butter surfaces to the top. The mixture should reduce to a thick dark red paste.
Add the mixed pulses and the ginger, season with salt and stir well, mashing a few beans while you do so. Cook for 3 more minutes. Then pour in 125ml hot water from the kettle and let the hotpot stew for another 5 minutes. Scatter over the coriander and serve with plain rice, pitta bread or a jacket potato, and a simple green salad.