For best results in gongfu cha, brew in the traditional gaiwan or in a small teapot. Too high water temperature would burn the leaves, resulting in a bitter taste.
The appearance
Though the green and white-spotted orange doesn't exactly look appetizing, don't be alarmed! The mandarin is a green-skinned variety, and the aromatic citrus oils in that crystalize upon desiccation, leading to white spots. The same effect can be observed by squeezing the peel of most oranges, then leaving the surface to dry.
How to steep
Though one could attempt to drop the whole mandarin in a gaiwan or teapot, better results may be obtained by (carefully) cracking the peel open, so that the tea inside can better be exposed. Having been packed inside the mandarin, the tea has absorbed some of its aroma and can be used alone, but including pieces of the peel offers a special and tasty experience. Play around with proportions! It is not recommended to use this tea with open clay teaware (e.g. Yixing, Chaozhou clay), as the pungent oils may be absorbed and flavor all subsequent teas, unless this happens to be expressly desired.