1. Cut cauliflower into small flowerets. In 3- quart casserole or bowl, place cauliflower and water; cover with casserole lid or large plate. Cook at high (100% power) 6 to 8 minutes, until cauliflower is almost tender.
2. Meanwhile, cut broccoli into small flowerets. Add to cauliflower; cover and cook at high 8 minutes longer, stirring after 4 minutes, until vegetables are tender-crisp. Drain vegetables; let stand, still covered, while preparing sauce.
3. In small bowl, place butter or margarine and salt; cover with large plate. Cook at high 1 minute or until butter or margarine melts. Stir in flour until blended; then stir in milk until smooth. Cook, uncovered, 3 minutes, stirring after 2 minutes. Stir in mayonnaise and chili sauce. Pour sauce over drained broccoli and cauliflower. Toss lightly to mix.