- Cook cauliflower and broccoli until tender-crisp; keep warm in serving bowl.
- Meanwhile, melt butter in medium-size saucepan over medium heat. Blend in flour; cook, stirring, 1 minute.
- Gradually stir in soymilk, dry mustard and onion salt until smooth. Bring to boil; reduce heat and simmer 4 minutes, stirring frequently.
- Pour sauce over vegetables; add parsley and toss to evenly coat vegetables with sauce.