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There is a kraut cutter, a wooden board about 2 ft long with a diagonal blade. We used all the time when I was a child. We laid it on a large pot. You cut heads of cabbage in half and push it over the blade flat side down. Try google or an old fashioned hard ware.

You can be more efficient with a knife than any sort of kitchen aid attachment, which will require lots of prep, and slow going. A better bet for home use would be the shredder on a food processor. However, even then, while it will make quick work of shredding, you will have to cut the cabbage into smaller portions to fit into the processor...and, of course, empty the bowl relatively quickly. Anything more efficient than that will cost you a few hundred bucks. Maybe your best bet is some friends and sharp knives.

Haha, we were doing that every fall in my childhood in Siberia. We used an enamelled bucket and "sechka" https://65.img.avito.st/640x480/4526427565.jpg Splice a head of cabbage in big pieces with a knife, put them into the bucket until it is full, then smash it all with sechka. https://www.youtube.com/watch?v=LJ1HR9o4JGc - that guy is using another kind of sechka, but the principle is the same. I was able to fill about 30 three-liter jars in a couple of days being a kid so that'
s very effective way to deal with a cabbage (not speaking of using any kind of machine).

The device costs around $10-20 in Russia, I don't know if you will be able to find and buy it in your location though. At least now you know what to look for.

Do you have a food processor? Most food processors come with interchangeable blades including a blade for shredding. Put the shredder blade in, lock on the lid, cut the cabbage into wedges that will fit in the feed tube, power on, and feed in the cabbage. You may have to empty the work bowl a couple times, depending on how much cabbage, but it's the fastest way I know of.

Knife, shmife. You need a mulcher!

It is a $54 blower / mulcher from Home Depot. Get a new one so it will be cleanish. Quarter your cabbages then suck them up. Your bag will fill with cole slaw-to-be. Maybe wash it and set it aside for next year?

These things are merciless. They will chop your cabbages fine. Even if you use an old one and clean it first, the good thing about cabbage is that the pickling conditions naturally kill any bad germs. You can make sauerkraut by lining a ditch with hay, putting in the cabbages, then more hay, then covering it up. This is cleaner than that.

You can buy a cabbage shredder on amazon for $20

Or delis often use a deli slicer to finely slice lettuce

You mentioned a Kitchenaid stand mixer attachment. Kitchenaid used to make a shredder/slicer attachment that's very good for this usage. It had a wide hopper that could hold a quarter of a cabbage at once.

Unfortunately, the newer edition of this attachment has a smaller hopper and isn't suitable for cabbage, but the older style is still available from third party sellers.

Here's one example.
https://www.ebay.com/itm/Kitchenaid-RVSA-Rotor-Slicer-Shredder-Cones-Stand-Mixer-Attachment-New/163792960617

I'm good with a knife, and I sometimes use this for a single head of cabbage. It's definitely faster than hand slicing for anything more than two or three heads, even with setup and cleaning time. It also produces a very consistent cut.

It's definitely still going to require cutting up the cabbage heads first, and won't be as fast as some of the more expensive options, but it's an affordable alternative to the professional grade options.