Two most important elements of this recipe are preheated oven and lukewarm milk. Cold milk will make popovers dense and they will not rise as high. There is also a necessary step at the end, to let the batter rest before baking. It allows the gluten to relax and starch grains to swell resulting in much more light and fluffy popovers. Here is a link to Nonstick Popover Pan I recommend. You will need two pans to make this recipe.