You have to use Varoma temperature for steaming the vegies and chicken Melissa. I would use water in the bowl, vegies in the basket, chicken fillets in the varoma bowl and some vegies on the tray which don't need as much cooking (add them a bit later even). You can then put the potatoes back in the bowl and mash. I've never cooked potatoes in milk and steamed anything above on varoma but someone may have.
Have you seen
Baf's chicken and veg meal? Check it out, it's a good basic meat and veg meal.