Preheat the oven to 450°F, and thoroughly coat a popover pan with cooking spray. Place the pan in the hot oven and allow it to heat up while you make the batter (this lends to a crispy outer layer).
Break the eggs into a bowl and whisk gently. Stir in the flour, salt, milk, half-and-half, and melted butter until just barely blended; a few lumps are fine. Finally, whisk in the cheese. Let the mixture rest for 5 minutes. It will resemble a thin pancake batter.
Fill the popover pan wells ¾ full, and bake for 15 minutes. Very important: do not open oven door at all during the baking process. This will deflate the popovers!
Reduce the oven temperature to 350°F and bake an additional 20 minutes, or until the tops are brown and crusty.
Remove popovers from the oven, and make a small slit in their sides with a sharp knife. This helps some of the steam escape, which keeps them crispy. Serve immediately, or keep warm in a low oven. Serve with butter sprinkled with sea salt and pepper or jam