(The Best Recipe)
1 large egg
2 Tbsp unsalted butter, melted, plus extra for frying
3/4 cup milk
2 tsp vanilla extract
2 Tbsp granulated sugar
1/3 cup unbleached all-purpose flour
1/4 tsp table salt
4 – 5 slices day-old challah bread (3/4-inch-thick) or 6 to 8 slices day-old sandwich bread
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.
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.