Preheat the oven to 425°.: The oven should feel like a blast of dry heat when you open it, and the hot air is essential for creating immediate steam that makes the batter surge upward. You want an intensely hot environment so the exterior sets quickly while the interior expands. A common pitfall is not preheating long enough, which results in limp popovers rather than tall ones, so resist the urge to rush this step.
Add the popover pan or muffin tin to a sheet tray and preheat in the oven for 10 minutes.: The sight of the shiny tin warming through the rack is reassuring, and when you quickly place batter into a scorching metal cup it sizzles, signaling strong lift to come. The tray helps stabilize the pan and ensures even heat transfer. If you skip this or use a cool pan, the batter will stick and won't climb, so always preheat the metal until it is uniformly hot.
In a large bowl whisk together the eggs, butter, and milk until combined and smooth.: As you whisk, the mixture should become glossy and slightly thickened, with the melted butter fully incorporated and no streaks. The aroma will be dairy sweet and comforting. The reason for thoroughly combining now is to ensure even distribution of fat and liquid so pockets of unmixed butter do not create uneven rise. If lumps persist, it will affect texture, so stop and blend if needed.
Next in a separate large bowl whisk together the flour and salt until combined and then add in the wet ingredients.: The dry mixture should look uniform and pale, and when you pour the wet mixture in you will notice the batter initially look shaggy before smoothing out. Mixing in this order prevents pockets of salt or flour from forming and helps the batter hydrate evenly. A common mistake is overworking the batter at this stage, which can develop gluten and lead to tougher popovers, so mix just until combined.
Whisk until completely smooth and set aside. If you cannot get it completely smooth, add it to a blender and blend on high for 30 seconds.: When the batter is right it will fall from the whisk in a ribbon and show no lumps, with a consistency that is pourable yet slightly viscous. Blending ensures complete smoothness and helps incorporate more air for lift. If you skip smoothing, small flour pockets can expand oddly and create uneven interiors, so use a blender as a reliable rescue.
Take the preheated pan out of the oven and immediately spray with non-stick spray. Evenly pour in the batter until each cup is about 2/3 to 3/4 of the way full.: The hot metal will hiss when you spray it, a small reward that means the batter won't cling. As you fill, the batter should glisten and settle, and the level should leave room for dramatic rise. Overfilling leads to spills and underfilling yields short popovers, so aim for the 2 3 to 3 4 guideline.
Bake at 425° for 20 minutes and then at 325° for 10 minutes.: In the first phase you will see a rapid swell, with the edges turning bronzed and crisp while the centers remain soft and slightly bobbing. After 20 minutes lowering the temperature to 325° allows the interior to finish without burning the exterior, producing a tender crumb. A mistake people make is opening the oven early to peek, which drains heat and can cause collapse; avoid opening until the full bake time has elapsed.
Serve.: Once removed, the popovers should sound hollow when tapped and feel crisp on the outside while still warm inside. Serve immediately for the best contrast of textures, offering butter or a spread alongside. If you wait too long they will soften and lose that dramatic crispness, so plan to bring them to the table right away.
