Break the cauliflower and broccoli into florets and chop the cabbage into bite size pieces. Cook in lightly salted boiling water for 8 to 10 minutes, or until tender. Drain well and transfer into a flameproof dish. Mix together the yogurt, grated cheese and mustard. Season with salt and pepper. Spoon over the cauliflower, broccoli and cabbage. Sprinkle the breadcrumbs over the top and place under a moderately hot broiler until golden brown. Serve hot.
Recipe from Pennsylvania Vegetable Growers Association.