Preheat the oven to 450°F and position the oven rack on a lower shelf. (See Kelly’s Notes.)
Place the eggs in a bowl of hot water for 10 minutes.
Generously grease a standard 12-cup muffin pan all over (including the areas around the cups) with unsalted butter.
In a large bowl, whisk together the eggs, milk and salt until the mixture is well combined. Add the flour and continue whisking until the mixture is frothy. (There shouldn’t be any large lumps.)
Quickly whisk in the melted butter until combined then divide the the batter among the muffin cups, filling them 2/3 to 3/4 full.
Bake the popovers for 20 minutes without opening the oven door. Reduce the heat to 350°F (again without opening the door), and bake the popovers for an additional 10 to 15 minutes, until they're a deep, golden brown. (See Kelly's Notes.)
Remove the popovers from the oven, release them from the pan and serve immediately.