A popover seems like a magical delight when it pops “over” the edges of the pan.
Making popovers at altitude is a matter of trial and error — and a whole lot of errors — until it seems that you can get the ratios of eggs to flour just right so they expand, don’t deflate, and cook enough.
After a dozen practice batches we have learned the importance of:
1) sifting the flour before adding it to the mixture
2) an extra egg or at least half an egg
3) measuring the temperature in the oven (mine beeps when it’s not actually at temperature yet)
4) pre-heating the pans so that the batter sizzles when it hits the pan
5) hoping for a cloudy day (my popovers pop better on cloudy days than sunny days!)