You can add lots of flavors to sauerkraut (caraway, onion, garlic, mustard) but all you need is cabbage, salt, and time.
Ingredients
1 head napa cabbage, sliced thinly
salt
Method
After trimming and slicing the cabbage, weigh it
Calculate 2% of the weight in salt-- so if it is 500 g cabbage, you'd need 10 g salt etc
Sprinkle the salt over the cabbage and bash with a rolling pin or empty wine bottle until the cabbage has released enough of it's liquid to create a brine that covers the cabbage
Weigh the cabbage under the brine with a clean plate and leave at room temperature until it ferments, usually about 12-24 hours
Taste the kraut every day until it is the level of tang that you like
Jar up and put in the fridge to slow the fermentation and eat