Challah French Toast

From Cook's Illustrated, May 1997.

Though thick-sliced challah is best for French toast, you can substitute high-quality, presliced sandwich bread. Flipping challah is easiest with tongs, but a spatula works best with sandwich bread. To speed the cooking of large quantities, heat two or more skillets to brown a few batches at once. To vary the flavor of the batter, add three-quarters of a teaspoon of ground cinnamon or one-half teaspoon of ground nutmeg with the dry ingredients, or substitute almond extract for the vanilla.

Ingredients
1 large egg
2 tablespoons unsalted butter , melted, plus extra for frying
3/4 cup milk
2 teaspoons vanilla extract
2 tablespoons granulated sugar
1/3 cup unbleached all-purpose flour
1/4 teaspoon table salt
4 - 5 slices day-old challah bread (3/4-inch-thick) or 6 to 8 slices day-old sandwich bread

Instructions
1. Heat 10- to 12-inch skillet (preferably cast-iron) over medium heat for 5 minutes. Meanwhile, beat egg lightly in shallow pan or pie plate; whisk in butter, then milk and vanilla, and finally sugar, flour, and salt, continuing to whisk until smooth. Soak bread without oversaturating, about 40 seconds per side for challah or 30 seconds per side for sandwich bread. Pick up bread and allow excess batter to drip off; repeat with remaining slices.
2. Swirl 1 tablespoon butter in hot skillet. Transfer prepared bread to skillet; cook until golden brown, about 1 minute 45 seconds on first side and 1 minute on the second. Serve immediately. Continue, adding 1 tablespoon butter to skillet for each new batch.
3. Adorn your french toast with syrups, jams, butters, fruits, etc. Eat and swoon.