This recipe for spring rolls, or harumaki (春巻き) as they are call in Japanese, may not be authentic - or at least, not authentically Chinese. It’s authentically Japanese-Chinese, or chuuka  - Chinese dishes that were introduced to Japan mostly in the late 19th-20th centuries by Chinese immigrants (many of whom decided to stay), that have been adopted and adapted to Japanese tastes. Chuuka is not as heavily adapted as yoshoku  (western style Japanese dishes), but they do differ in varying ways from the originals. These are the spring rolls I grew up with, the way my mother made them. (As I’ve stated here before , I don’t really feel capable of covering the entire spectrum of ‘Asian’ cooking, so in that category I mainly stick to the Japanese, Japanese-Western (yoshoku), Japanese-Chinese (chuuka) dishes I know.)
Spring rolls are quite easy to make as long as you break the steps down. First you need to make the filling and let it cool down. You could even use leftovers, and it’s fine to make the filling several hours in advance or even the day before. Next you need to wrap the rolls. Finally, you fry them. You can do the make-the-filling step some time in advance, but the rolls do need to be wrapped just before you fry them or the skins may become soggy.
I also recommend using readymade spring roll wrappers, which are made from white flour and water. These are available at any general Asian, Chinese or Japanese market, in the freezer section. They’re about 9 inches (23cm or so) square, so you can’t mix them up with the smaller shumai or gyoza (potsticker) skins. Making paper-thin spring roll wrappers from scratch takes spring rolls out of the realm of something you could conceivabley make for an everyday dinner to an epic, complicated task that should only be attempted when you have a whole weekend afternoon to spare.
All the vegetables should be cut so they are about 7 cm / 3 inches long.
For 10 to 12 rolls (or however many wrappers come in your packet):
For the filling:
salt and pepper
1 packet readymade spring roll wrappers
If your spring roll wrappers are frozen, make sure you defrost them completely, in the packet, before trying to separate them, or they will rip. Keep unusued wrappers covered with a damp cloth - they dry out rather fast.
Heat up the sesame oil in a wok or frying pan over medium heat. Add all the shredded vegetabeles and stir fry until crisp-tender. Add the cooked meat, soy sauce and sake. Taste and add salt and pepper to taste.
Add the water in which the cornstarch or potato starch has been dissolved. Stir until the liquid surrounding the vegetables and meat has thickened and is transparent rather than cloudy. Take off the heat and let cool. Divide the filling into 10 or 12 portions, as many as you have wrappers.
Place a wrapper diagonally, so a point is facing you. Put some of the flour-paste you’ve made on the two sides that are away from you. Put a portion of the filling fairly close (but not touching the edges) of the point closest to you. The key is to not overfill - if the sauce/liquid of the filling leaks out, your rolls may burst during frying.
Start rolling up, folding in the sides along the way - try to roll tightly, so that little air gets trapped. When you are done, the rolls should look like this:
Heat the frying oil to around 140°C (284°F) - a fairly low temperature. If you’ve ever made french fries (chips) at home, this is about the temperature you fry the potatoes in initially, to cook them through but not brown them. If you don’t have a fryer or a kitchen thermometer, you can gauge the temperature by putting in a piece of raw potato; it should cook but not brown.
Put the spring rolls in gently, 2-3 at a time. They should brown gradually, turning very crisp on the outside and molten hot on the inside. You do not want the surface to become bubbly and mottled as you seein some restaurant spring rolls. You want it to be perfectly smooth and light.
Drain the spring rolls well. I use a flat woven bamboo tray kind of thing lined with newspaper, with kitchen towels on top.
You can eat the spring rolls as-is, or with mustard and soy sauce (karashi joyu) - plain mustard powder that’s reconstituted to a paste, mixed into soy sauce. (Colman’s Mustard powder will do fine. Don’t use a prepared vinegary mustard.) Best served piping hot, though they are quite delicious cold too. We usually pretend we can stop at just 1 or 2 as appetizers. (Never happens.)