In a large mixing bowl, beat eggs and egg white on medium speed until pale and frothy (about 3 min.). Meanwhile, heat milk in the microwave or in a saucepan on low heat until just warm to the touch. Add milk to the eggs; beat until combined (about 30 sec.). Add warm butter; beat until combined (about 30 sec.). Reduce speed to low; add flour and salt, mixing just until batter is the consistency of heavy cream and lightly bubbled (about 30 sec.). Let batter rest at room temperature, covered, for 30 min. Prepare two 6-cup popover pans by placing ½ tsp. clarified butter in each cup. Set pans, loosely covered with foil, on a baking sheet in a preheated 425° oven; heat for at least 15 min. Pour batter into a container with a spout. Remove the baking sheet with hot popover pans from the oven; discard foil. Carefully pour batter into the popover cups, filling each just less than 2/3 full. Return baking sheet with popover pans to the oven; bake without opening the oven door for 25 min. Reduce heat to 325°; continue baking until popovers are golden-brown (14-18 min.). Remove pans from the oven; let rest for 1 min. Gently lift popovers from cups; serve immediately.

CLARIFIED BUTTER: Cut unsalted butter into small pieces; melt in a saucepan over low heat and simmer, undisturbed, for 10-15 min. (do not allow the butter to sizzle until the fats separate). Strain the mixture, discarding the white milk solids and retaining the clear yellow clarified butter.