@@mikunakano2226 it doesn’t need long to preheat. I just put the pan in the oven before I turned it on, and by the time the oven is preheated the pan is plenty hot. I haven’t personally tried different flours than all purpose for these, it might change how well they “popover” when baking if a different flour is used. Bread flour might rise but I expect they won’t be as soft, something like cake flour they might be too soft and not enough structure to keep it from deflating after baking. It actually sounds like a fun experiment…