To make the spicy black beans, rinse the beans and put in a medium pan with the six cups of water and kombu, then bring to the boil. Reduce the heat and simmer for 30 minutes or until the beans are tender. Remove the kombu, drain the beans and set aside.
Dry-roast the cumin, coriander and mustard seeds. Once they start to pop, remove from the heat and grind to a powder with a mortar and pestle or spice grinder.
Heat the oil in a large pan and saute the onion, garlic and chilli until the onion is soft. Add the spices and cook for a further two minutes. Add the tomato puree and 1/4 cup of water and stir until well combined.
Crush the tomatoes, add to the pan with the beans and simmer for 40 minutes until the bean mixture is quite thick and the liquid has been almost completely absorbed.
While the beans are cooling, prepare the salsa. To make the salsa, steam the corn cob for 3 minutes. Rinse in cold water then cut off the kernels. Mix the capsicum and coriander in a bowl with the corn kernels, capers and lime juice. Refrigerate until ready to serve.
Serve with a dollop of yoghurt mixed with the chives.