Thinking outside the omelet—both sweet and savory.
Position rack on lowest level of oven. (Take out the other rack so there’s headroom for the popovers when they rise, if necessary). Preheat oven to 425° F.
Place either 6 standard ¾ cup (Pyrex) glass custard cups on a jelly-roll pan or a 6-cup popover pan (the Williams-Sonoma model, for example) in the oven and allow to heat while mixing above ingredients.
If you do not have the patience (like me) of waiting until eggs and milk reach room temperature, fill saucepan with the hottest tap water (just stick the saucepan in the sink) and submerge the eggs and milk (I pour it into a glass) in to hot water to warm. In about 10–15 minutes they are both room temperature. Eggs and milk should not be cold or popovers will not rise as high.
Put eggs in bowl. Beat eggs until frothy, add milk and butter and then flour and salt (sift while you add to the liquid mixture). I make sure everything is mixed smoothly (no lumps), and then I beat them with a hand mixer or manual mixer until they have plenty of air in them.
I then take the popover pan/cups out of the oven, put it on the counter or wooden board (no burning of counters allowed), grease the cups quickly (you can use cooking spray) and pour the popover mixture evenly into each of the six cups.
Place the pan/cups in the oven for 25 minutes at 425°; after 25 minutes, lower to 350° and bake another 20 minutes. Do not open the oven until the popovers are fully baked.