How to remove popovers without sticking.

I have found that it is hard to remove popovers from the pan without having them stick. Should I remove them when they are hot or cool?
—H.B., Boston, MassachusettsFor best results, use a heavy metal popover pan rather than muffin tins or custard cups. Lightly grease the popover cups, then dust with flour, sugar or grated Parmesan cheese. The batter will cling to the sides and produce better results.
Loosen popovers from baking cups by running a knife around the edge, then remove immediately.