Cabbage leaves: In large scale productions, you boil an entire large head of cabbage and then separate the individual leaves. For my small scale production and small-sized cabbage rolls, I separated each cabbage leaf by first cutting into the bottom veins and then using running water (introducing it between the leaves), to separate each leaf without tearing it. (I prepared 4 leaves). I used a rather small head of cabbage. I boiled the leaves in a large pan with salted boiling water for 10 minutes covered with a plate which fit snugly inside of the pan to keep all the leaves submerged during cooking. After the leaves were cool enough to handle I shaved off the large veins toward the bottom of the leaves without cutting through them (the #1 image below in the right back).
Stuffing: I finely minced onion (1/3 medium), carrot (1/2 medium), garlic (1 clove), and ginger (one thin slivers) which I sauteed in vegetable oil for few minutes and seasoned with salt and pepper and set aside to cool. You could also add shiitake mushroom, finely chopped, but I did not have one.
For the meat, I used trimmings from a pork tenderloin. I hand chopped it into ground pork (about 200 gram, I guess. The image #1). I mixed in the vegetables above,with bread crumbs (1/4 cup, I use panko, moistened with milk, the image #1 below in the left back). I added an egg (1 large) and seasoned it with freshly ground nutmeg, salt and black pepper. I mixed it well until the stuffing become elastic and hung together.
Assembly: As seen in the image #2, I made a small cylinder and placed it closed to the root end of the precooked cabbage leaf and rolled with the both side tucked in and made four rolls. Try not to over stuff the cabbage (the image below #3). (I had some stuffing left over. I made small patties and cooked it like a hamburger and braised it with mirin and soy sauce in teriyaki style. I served it with the side of a Japanese coleslaw. I forgot to take a picture)
Cooking: I used a Japanese-Western hybrid broth. I used Swanson non-fat reduced salt chicken broth and added bay leaves, sake, whole black pepper corns and a half a carrot (left over from the above). The cabbage rolls should fit snugly submerged in the cooking liquid (the image below #4). Of course, you could cook the cabbage rolls in "Oden" broth or tomato sauce if you like. On a very low flame, I gently simmered it with the lid mostly on and when it started boiling, I set the lid slightly askew and cooked for 40-50 minutes (I added more sake in the middle to compensate for the evaporation).
Two days later, we reheated the cabbage rolls with snap peas. It tasted even better.