I'm making a stir fry tonight with scallops, broccoli, mushrooms, sweet potatoes, snap peas and cuke. I think I need to pre-steam the broccoli and sweet potatoes, but I'm not sure how long so that they are cooked, but not mush when everything else is ready. What's best -- 2 minutes? five minutes? I don't want to just stir fry them sooner, as I use very little oil and it will be very (very!) hot, so the chance of these two veggies cooking that way without burning is slim. Thoughts?