Place a popover pan in the oven and heat until oven and pan reach 350. Gently warm the milk over low heat and set aside. Whisk the eggs until frothy and slowly whisk in the milk (so as not to cook the eggs). Set the mixture aside. Sift the flour with the salt. Slowly add the dry mixture and gently combine until almost smooth.
Once combined, remove the popover pan from the oven and spray with non-stick vegetable spray. While the batter is still slightly warm or at room temperature (not cool), fill each popover cup 3/4 full. Top each popover with 2 1/2 Tablespoons for grated gruyere.
Bake at 350 for 50 minutes, rotating pan half a turn after 14 minutes of baking.
Remove from oven, remove popovers from pan and serve immediately.
They serve with an herb butter and slightly coarse sea salt. Yum!