If you are using thick cut meat, such as pork for tonkatsu or ginger pork, make several cuts in the meat or pound it to break down the muscle fibers.
If you are using a whole piece of chicken thigh or breast, make several cuts in it in the same way. Poke several holes into the thick parts with a fork so that the enzymes will penetrate the meat easily.
When slicing meat, it's a good idea to cut it perpendicular to the direction of the muscle fibers to make the meat more tender. If, on the other hand, you want to retain the texture, slice it in the direction of the muscle fiber.
Cut out the core of a cabbage and grate it. To grate just a little, use the method described in Recipe ID: 2322784 to reduce waste.
Sprinkle the meat with a little sake and the grated cabbage core. For thinly sliced meat, rub the mixture in well.
Cabbage doesn't get in the way of other flavors, so for stir fries or grilling, you can just cook the meat as-is. It actually makes it more tasty.
Leave the meat marinating in the cabbage core for more than 15 minutes. The longer you can leave it in, the more effective it is, so prepare it in the morning to use the meat for dinner, or prep it at night to use the next day...and so on. Do it when you have some extra time.
After it has marinated, cook the meat as-is. Here I used the meat for tonkatsu, so I wiped it off quickly, then proceeded with my usual method for making tonkatsu.
Story Behind this Recipe
Many people know that enzymes that break down proteins help to tenderize meat. The best known foods with those enzymes are pineapple and kiwi, but it's quite an effort to buy and prepare them just for this purpose. I did some research on what other foods have these enzymes, and what do you know, cabbage has them too!
You can tenderize meat in the preparation stage before you start cooking it. The cabbage must be grated, not chopped! If you have a pineapple or kiwis around they work faster, but their flavor does get in the way of other flavors. So if you have the time, use cabbage!