I learned to make mandu - Korean dumplings that can be steamed, boiled, pan-fried or deep-fried - from a Korean friend, who insisted on making her own wrappers. It's not difficult, but it does take a little more time, so I wouldn't blame you if you use purchased wrappers. Buy the round wrappers (often labelled for sui gau, jiaozi or gyoza), and if you have the choice of thin or thick, choose the thicker ones. You'll need about 50.
If you do make the mandu wrappers, the work will go a lot faster if you use a tortilla press or a dumpling wrapper press (which is smaller than a tortilla press), instead of a rolling pin. The dough is a little damp, so after shaping the wrappers, and when you fill the dumplings, don't let them touch, or they'll stick together.
It's important to squeeze as much water as possible out of the kimchi and bean curd - if you don’t, the moisture will make the dumpling wrappers soggy.
The ideal kimchi for this dish is the old stuff that's been neglected in the back of your fridge - it has a stronger, more sour taste than kimchi that's been made recently. It's fine if you have only young kimchi, but the flavour won't be be as strong.
Make the dough by mixing the water with the flour to form a rough, shaggy mass. If the mixture seems dry, drizzle in more water. Turn the dough onto a lightly floured work surface and knead it for several minutes until it becomes cohesive and smooth. It should be neither sticky nor dry. Place the dough on the work surface, cover with an inverted bowl and leave it at room temperature while making the filling.
Cut the tofu into large chunks and pat them dry with paper towels. Dampen a clean kitchen cloth and squeeze out as much water as possible. Put the tofu in the centre of the cloth, pull up the corners and edges to form a bag and squeeze it tight to extract as much liquid as possible. Put the tofu in a bowl.
Rinse the cloth and squeeze it dry, then repeat the process with the kimchi. Weigh out 130 grams (4⅓oz) of the kimchi then roughly chop it before putting it in the bowl with the tofu.
Mince the chives, spring onions and garlic and add them to the bowl. Add the minced pork, the salt, pepper and sesame oil and mix thoroughly. Shape a small amount of the mixture into a meatball and pan-fry it until cooked through. Taste the meatball and adjust the seasonings, if necessary. Refrigerate the mixture while making the dumpling wrappers.
Line a baking tray with aluminium foil. Have a small bowl of water ready for moistening the edges of the wrappers.
Unwrap the dough and cut it into two even pieces. Wrap one piece of the dough while working with the other. Roll the dough into a long snake then cut it into pieces that each weigh 15g (½oz). Use a tortilla press or dumpling press to shape the dough pieces into a wrappers about 9cm (3½in) in diameter - they will be a little thicker than commercial wrappers. (Or use a small rolling pin to roll out the dough.) Make about 10 wrappers at a time before filling them, placing them flat on the work surface so they aren't touching each other.
Spoon some of the filling into the centre of a wrapper (stuff it quite fully). Lightly moisten half of the wrapper then fold it over to tightly enclose the filling, pressing out any excess air. Firmly pinch the edges of the wrapper to seal it. Bring the two corners of the half-circle together, moisten one of them, then press them firmly so they adhere – they’ll look like fat tortellini. As you wrap each dumpling, lay it on the foil-lined baking tray, but don’t let them touch each other. You'll have about 50 mandu.
After shaping all the dumpings, bring a large pot of water to the boil. Cook the dumplings in batches, leavaing them plenty of room to swim in the pot. When you first place them in the water, they’ll sink. After they float to the surface, cook them for two minutes. Scoop the mandu from the water with a flat, slotted ladle, shake off the excess water, them put straight into individual serving bowls.
Heat the chicken broth until simmering and season with salt, if necessary. Ladle the broth over the mandu.
Drizzle each portion a little sesame oil and sprinkle with spring onions. Serve with banchan.