In large saute pan, wok or skillet, heat the canola oil over high heat. Add cauliflower and cook for about 2- 3 minutes. Add all remaining veggies except water chestnuts and green scallion tops and stir frequently. Cook for about 5-6 minutes.
In a small bowl, mix soy sauce with sesame oil. Add to the skillet with water chestnuts and green scallion tops. Serve immediately.