Take off the outer leaves of the cabbage until you reach fresh light green leaves. Cut the cabbage in two and with a knife take out the core, leaving the cabbage with a wedge shaped space in each half. You can either thinly slice the cabbage using a very sharp knife, or you can use the shred tube of a food processor. Place the shreds in a large ceramic bowl.
Shred your carrot in a food processor or grate it using the largest holes on a box grater because you want to be able to see the pretty color of the carrot throughout the slaw.Place the carrot shreds in the bowl with the carrots. If using onion,peel and chop 1/2 the red onion. OR, for low fodmap, chop the light green stems of several scallions and a small bunch of chives. Sprinkle the chopped onion or scallion stems and chives over the shredded cabbage and carrots.
In a small ceramic bowl whisk together the rest of the ingredients: the oil, vinegar,mayonnaise, sugar, salt and pepper. Taste for seasoning. Then pour this dressing over the cabbage mixture in the bowl and toss together until everything is well coated with dressing. Cover the bowl and refrigerate until ready to serve.
You can serve it set on a large butter lettuce leaf or just alone on a small salad plate, or in a gorgeous bowl on your buffet or picnic table.
Try not to eat it all yourself while making it because the dressing combination is extremely addictive and while you are gobbling it up you tell yourself that cabbage is calorie free and good for you. However, sadly, mayonnaise is not! Happily, small portions are fine.