Add the flour and salt to the work bowl fitted with the metal blade and process 5 seconds. If you have a 1- or 2-quart glass bowl with a pouring spout, break the eggs into it and whisk to combine the yolks and whites well. Whisk in the milk and butter. Lacking such a bowl,
combine the eggs, milk, and butter the same way in a medium bowl and transfer to a pitcher.
Start the processor, and take about 10 seconds to add the liquid through the feed tube. Process 5 seconds more and stop the machine. Scrape sides of work bowl well, making sure to dislodge any flour, and process 10 seconds more. Total processing time is 30 seconds or less.
To make the batter with a wire whisk, combine the flour and salt in a large bowl. Add about 1 cup of the liquid and whisk well. Batter will be thick. Gradually whisk in remaining liquid, about ½ cup at a time. Do not overbeat. The batter should not be bubbly.
Strain the batter into a bowl with a pouring spout or into a pitcher. If baking right away, let the batter stand while you prepare the baking cups and preheat the oven. If baking the next day, cover the batter container tightly with plastic wrap and refrigerate.
Butter or coat with cooking spray the pottery cups or a 6-cup popover pan. You’ll have extra batter if using the popover pan; cover and refrigerate to bake later.
Adjust an oven rack to the lower third position and preheat the oven to 400 degrees. If using pottery cups space them well apart on a large (17 x 11-inch) rimmed baking sheet.
Divide the batter evenly among the cups, filling them to with ½-inch of the rim, and place in the oven.
Bake 20 minutes at 400 degrees, then reduce the temperature to 375 degrees and continue baking about 35 minutes longer for 4-ounce cups or 45 minutes longer for 6-ounce cups or for popovers baked in a metal pan.
Do not open the oven door once the popovers are in the oven.
Oven temperatures can vary wildly, so check the popovers about 10 minutes or so before the baking time is up to see how brown they are. They should be very well-browned—peek through the glass on the oven door. Be sure not to underbake or the popovers will be soft and collapse after you take them out of the oven.
When the popovers are done, open the oven door and reach in with a sharp paring knife to stab the top of each one quickly in two or three place to release the steam. Close the door and bake 5 more minutes.
Take the popovers out of the oven and remove them from their cups. Set them in a napkin-lined basket and serve as soon as possible with plenty of butter, honey butter (1 part honey mixed with 2 parts butter) and any jam or preserve you like.