The Net is full of recipes and suggestions, and tips on what is really important for making great popovers. Here's what has finally worked for me.
First, spend ~$100,000 on home renovation, especially including an oven like our new DCS. This thing has the most intuitive digital controls I have ever seen on any device. But much more importantly, it is a convection oven with precise, and apparently accurate heating. I don't know if the convection part is important, but high, even heat makes a big difference for popovers. 430 degrees F is too low: they don't pop well, yielding what we call "dough boys". These are eggy and tasty, but not popovers. The renovation may include granite countertops, the granite coming from Brazil, but apparently not containing detectable amounts of thorium. But that is another story.
I've tried many recipes, but none have worked better than the one that came on the genuine popover tins, with slight modifications that I have included:Mix the wet stuff together, then slowly blend in the flour. Let it warm to room temperature, but don't overdo it, because salmonella can grow in them thar eggs. One friend suggested that the secret is to let the batter sit over night. Leave it in a fridge.
This is vital. Freshly-made batter won't pop, unless there is Wondra in in. (See below.).
It's important that the ingredients be at or near room temperature. Coldness is bad.
Preheat the oven, with the well-buttered pans in there warming with the oven. This will cause a lot of smoke when you open the door. Turn off the smoke alarm. (We have our kitchen smoke detector on a switch now.)
When the oven reaches working temperature, fill the cups with batter. The fuller the cup, the larger the pop, but if a full cup doesn't pop, it will bubble over.
My recent successes run for 20 minutes at 455-460, just on the edge of burning them, then 20 minutes at 350. Don't open the oven. "No peeping" says one recipe (Joy of Cooking?)
Popovers are incredible with a scoop of high-grade vanilla ice cream in them. In my dotage I will start a chain of stores at the Jersey shore that sells these.
It's not every day you see a recipe for food that includes the words "thorium" and "salmonella".