This Japanese tabletop-cooked dish is less a recipe and more of a guideline; you can use whatever seafood (and other ingredients) you like. Most people think of hotpot as a winter dish, but because this recipe uses dashi broth instead of a heavier soup, it's light enough to eat throughout the year.
For the broth for this dish, I use a dashi bag. These are sold in the Japanese section of supermarkets, and are easy to use - they only need to be soaked in hot water for a few minutes to make an umami-rich broth. If you don't have a dashi bag, subsitute a light, unsalted seafood broth.
This amount of ingredients is plenty for two diners, but you can easily scale up to serve more people. I don't serve this dish with a dipping sauce, but if your guests insist, you can add a Cantonese touch by mixing chopped red birds-eye chillies (or another type of hot chilli, such as serrano) with soy sauce, and serving the sauce in small individual bowls. Be sure to put a large bowl on the table for empty shells.
Scrub the crabs under cool, running water. Just before cooking them, poke a sharp metal skewer between the eyes into the brain, to kill them. Rinse the prawns and clams and put them in a colander to drain. Slice the fishcakes, and cut the bean curd into four pieces. Cut the Chinese cabbage in half lengthwise and trim off and discard the core. Slice the cabbage into 2cm (⅞ inch) pieces. Cut the negi on the diagonal into 1cm (7/16 inch) pieces. Trim off the bottom part the enoki mushrooms, and break them and the shimeji mushrooms into clumps.
Pour 500ml (2 cups) of water into a clay or cast-iron pot that holds about 2 litres (2 quarts). Bring to the boil over a portable burner, then add the dashi bag and leave to soak for a few minutes. Remove the dashi bag from the pot.
Simmer the seafood, putting the ingredients in the pot according to how long they take to cook. Start cooking the crabs first, simmering them for about three minutes before adding the prawns. Let the crab and prawns cook together for a few minutes, then add the clams, fishcake, bean curd, cabbage, negi and mushrooms. If the pot is too full, cook all the seafood together first and eat it when it’s ready; when there’s room in the pot, add the bean curd and vegetables. Adjust the flame of the burner as needed (or turn it off altogether) so the ingredients don’t overcook. If too much liquid evaporates, add some water.
After eating most of the ingredients, add the udon noodles to the pot and simmer until done. Eat the noodles and remaining ingredients with the broth.