You could really use any combination of vegetables but I like to get some crunchy ones in there.
Also I don't measure because it depends on how many people you're making it for and your own taste. As for the sauce, I really eyeball it and then just try it to add more. Of course the homemade methods work much better.
Start by heating up just a tiny bit of oil in a non-stick skillet. Add onion, garlic, bay leaf and cumin seeds. Cook until onion is translucent. Add the parsnips and cook until almost done. Add the radish, cook for a few minutes and then add the: boy choy, red pepper, celery and leek. Cook until mostly done then add the sauce and finally the bok choy greens at the very end.
You can easily play around with this. It's a mix of sweet & sour/teriyaki sauce flavor. I suppose if you want it thick you could probably add some arrowroot.
I hope you enjoy!