Preheat convection oven to 350°. Sift flour and salt together into a medium bowl and set aside. Put eggs into the bowl of a standing mixer with a whisk attachment. Beat eggs on medium-low until frothy and slightly thicker, about 3 minutes. Increase speed to medium-high and beat eggs until thickened, 1–2 minutes more. Increase speed to high and beat eggs until very thick and foamy, about 2 1⁄2 minutes more. With the motor still running, add half the milk and mix until well combined. Then add half the flour mixture and mix until well combined. Scrape down bowl. Repeat process with remaining milk and flour mixture. Strain batter through a fine-mesh sieve into a large bowl. Set aside to let rest for 5 minutes, then skim off and discard any foam that rises to the surface.
Generously spray the insides and edges of 12 (2⁄3-cup) nonstick popover tins with cooking spray. Divide batter among the tins (tins will be just shy of full). Carefully top each popover with 2–3 tbsp. cheese, making sure that the batter doesn't spill over the edges. Gently put the tins into the oven and bake, rotating tins halfway through, until popovers are deep golden brown and puffed, about 50 minutes. Popovers may be eaten immediately or allowed to cool on a wire rack and then reheated in a 350° oven.