1 tablespoon unsalted butter plus extra for greasing the pan
3 large eggs
1 cup all-purpose flour
1/2 teaspoon salt
1 cup milk
3/4 cup cheddar cheese freshly grated
1/4 cup chives finely diced
Preheat the oven to 450°F, and thoroughly grease your muffin or popover pan.
Melt the tablespoon of butter in your bowl and set it aside to cool slightly.
Break the eggs into the same bowl (with the butter) and whisk gently. Whisk in the flour, salt, and milk until just barely blended; a few lumps are fine.
Add in the cheddar cheese and chives and, using a rubber spatula, gently fold the cheese and chives into the batter. Don't over mix.
Fill the cups 2/3 full and bake at 450 degrees for 15 minutes. Then, reduce the oven temperature to 350 degrees and bake for an additional 20 minutes.
(Do not open the oven! Opening the oven door in the first 20 minutes can cause them to collapse.)
When they are brown and crusty, remove them from the oven, and make a small slit in their sides with a sharp knife.