Adjust oven rack to center position and heat oven to 425 degrees.

Lightly grease a 6-cup popover pan with duck fat including rims of pan.

Whisk the eggs until frothy. Whisk in milk.

Sift flour and salt into the liquid. Whisk for 30 seconds, until smooth. Then whisk in melted butter. Set the batter aside for 15 minutes.

When ready to bake, whisk the batter again and then pour batter into popover pan, dividing evenly, approx. 2/3 full.

Bake the popovers for 25 minutes, then reduce heat to 350 degrees and bake for an additional 10. minutes; do not open the oven to check on them before the 35 minutes have elapsed. When done the popovers will be tall, domed, and have a rich golden-brown color.

Remove the pan from the oven and use a sharp knife to poke a small hole in the top of each popover so the steam can escape. Allow them to cool in the pan for a minute or two, then remove them. They should pop right out.