Don't use regular cabbage for this recipe--it's too bitter. Napa cabbage is much milder and sweeter, but it still has the cabbage characteristic of not wilting in dressing. Napa cabbage tends to come in huge heads, so two of them were enough for an expected number of 50. People don't tend to eat a lot of salad at a buffet, I've found. I pre-shredded the cabbage the night before and stored it in plastic bags in the fridge. I think I ended up wasting too much of it, as I usually don't include much of the ribs, but sliced thinly they're fine. I usually just use the leaves, but next time I'm going to be more frugal. Sometimes when you slice into the cabbage it's all brown in the middle, and there are often brown spots here and there, so you will have to do at least some discarding. Granny Smith apples work well, diced into 1/4" pieces, as many as you like, and some chopped walnuts. The dressing couldn't be easier, with just four ingredients: I like to try to match the vinegar in the dressing to the salad, so for this one I used cider vinegar. If I'm making the dressing for, say, a strawberry-spinach salad, I like to use raspberry vinegar if I have it on hand. Otherwise red wine vinegar at least makes the dressing pink.