In a small bowl, whisk together the eggs and milk.
In a separate medium bowl, sift together the flour and salt and make a well in the center.
Pour the egg and milk mixture into the well and whisk together just until the liquid is incorporated. small lumps are not a problem.
Let the batter stand for 10 minutes.
If available, pour the matter into a bowl or measuring cup with a spout; this makes it so much easier to pour the batter into the muffin tins.
Working as quickly as you can, so that the pan does not cool down, pour the butter into the hot muffin tins to cover the bottom.
Using a pastry brush, give it a quick brush up the sides of the muffin cups.
Then quickly pour the batter evenly into the muffin pans.
A ring of melted butter floating on the batter is normal and necessary at this point.
Quickly return the pan to the hot oven and bake for 15 minutes.
Reduce the heat to 375°F and bake for an additional 15 - 20 minutes.
The puddings should be a deep golden brown.
It is very important not to open the oven door at any point in the baking time or you risk your popovers falling.
Remove from oven and let rest for only a couple of minutes before removing them from the pan. and serving.
Notes
To complement the Proper English Yorkshire Pudding, serve with completecomfortfoods.com's recipe for French Onion Braised Beef Brisket: https://completecomfortfoods.com/french-onion-braised-beef-brisket/