I finely dice the onion and about a quarter of a small cabbage, then add grated carrot, I always make sure there is plenty of carrot. I stir in one table spoon of mayo, I use organic, and that's it, it takes about 10 minutes to make from start to finish.
I store it in an air tight container in the fridge for a couple of days. It might last longer than that, I don't know, cause it never lasts that long! Best of all? Because I bought the ingredients I know it's 100% organic. If you have the garden and the time to grow your own, even better.
Sometimes I change things a little by using red cabbage or red onion. Spring onions are a nice change too. Chives are a nice addition, fresh is best, but dried will do if you can leave it to sit for an hour or two before use. How about big juicy sultanas?