Quite a while ago I posted a similar image named Ice Donut (see my gallery), where the main torus was completely glass. The render on that one took an insanely long time because I was rendering in the background and simply because refraction is so difficult a process. Nevertheless, at the time, someone suggested I should try a different computer platform for a better render speed. My response was that if the donut had been reflective instead of refractive, it would have taken FAR less time. Anyway, I finally got around to revisiting that image, put a reflective surface on the donut, and sure enough it rendered relatively fast, something like 20 to 30 minutes. Oh, and I changed the color scheme a little too -- and I liked the result so much I thought I'd post this one as well. Enjoy.