Preheat the oven to 450°F and place a 6-cup popover pan inside.
Combine the eggs, milk and butter in a blender and blend for 15 seconds to combine. Add the flour and salt and blend for another 15 seconds, scraping down the sides of the blender, if necessary. Add the cheese and fold in with a Flexible spatula.
Remove the hot pan from the oven. Grease it with nonstick cooking spray or brush with melted butter.
Evenly pour the batter into the cups; each one will be about 2/3 full.
Bake for 15 minutes and reduce the heat to 350°F and bake for another 15 minutes. Do not open the oven for the entire baking period.
Remove the popovers from the pan and transfer to a wire rack as soon as you take them from the oven. They should slip out easily, but if they do not, run a small paring knife around the edges of each popover. Jab each one with a small paring knife, to release steam.
Popovers are best eaten the day they are made and ideally within minutes of being pulled from the oven.