In a one-quart microwavable casserole, combine all the ingredients except the cornstarch, sesame oil and vinegar. Stir to coat well, cover and microwave on high heat 4 to 5 minutes; stir once halfway through cooking.
In a small bowl, combine the corstarch with 1 tablespoon of water, stirring to dissolve the cornstarch completely. Add it to the vegetable mixture along with the sesame oil and vinegar. Stir well, then cook 1 to 2 minutes more, until the sauce is thickened. Serves 4.