1. Melted butter, for greasing popover cups.
2. Position a rack on the lowest rung of the oven and preheat the oven to 425ºF.
3. Butter or spray nine ¾ cup glass custard cups or ten ½ cup muffin cups. If you're using custard cups, place them on a jelly-roll pan, leaving space between each cup. If you're using muffin pans, you'll need to use two 12-hole tins because you won't be filling all the muffin cups to give the popovers ample air circulation.
4. Pour all the ingredients into the container of a blender and whirl until smooth. (This can be done in a food processor or in a bowl using a hand-held mixer). Strain the batter if it is at all lumpy.

Baking the popovers:

1. For the custard cups, pour 1/3 of the batter into each cup, dividing any extra batter among the cups.
2. For the muffin cups, use ¼ cup of batter for each cup, filling alternate cups in each tin so that every popover has puffing space.
3. Bake, without opening the door, for 25 minutes, until the popovers are puffed, nicely browned, and crisp on the exterior.
4. Turn the temperature down to 350ºF and bake for another 15 to 20 minutes, to help dry out the interior, which, no matter what you do, will always be a little doughy in the center. (Some people love this part, others pull it out).
5. Serve immediately.

Storing:

1. Popovers are at their puffiest right out of the oven.
2. You can hold them at room temperature for a few minutes, or wrap them airtight, freeze them for up to a month, and reheat them in a 350º F oven for 10 to 15 minutes, and they'll taste good, but never as good as freshly baked.