This is the way I do it, usually when we have guests. I've never had any complaints. I do
make my own challah, but I'm sure store-bought would do just fine. Also, I'm not a big fan of cinnamon or nutmeg, but you might want to add a 1/2 tsp. of either to yours.
French Toast for Challah
1 large egg
2 tablespoons unsalted butter, melted,
plus extra for frying
3/4 cup milk or half and half
2 teaspoons vanilla extract
2 tablespoons sugar
1/3 cup all-purpose flour (I use Wondra
1/4 teaspoon salt
4 3/4-inch-thick slices day-old challah bread
Heat 10- to 12-inch skillet (preferably cast-iron) (or use an electric griddle at 325*), 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 over saturating, about 40 seconds per side.
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.