Best Ever French Toast

Our friend, Shel, brought a loaf of Challah ( an egg bread) to our potluck and swore the leftovers made the best French toast. He was right- it was the best I've ever had. Here is a recipe from "the Best Recipe" by the editors of Cook's Illustrated Magazine. I don't like a bunch of flavorings in my french toast so I omitted the vanilla, but did use vanilla sugar.

1 large egg
2 Tb. unsalted butter, melted, plus some for frying the bread
3/4 c. milk
2 tsp. vanilla extract
2 Tb. sugar
1/3 cup all purpose flour
1/4 tsp. salt
4-5 slices day old challah, 3/4 inch thick

Heat a 10 or 12 inch skillet over medium heat for about 5 minutes.
Meanwhile, beat egg lightly in a shallow pan or pie plate, whisk in melted butter, then milk and vanilla, and finally the sugar, flour and salt. Whisk until smooth.
Soak bread, but do not over saturate, about 40 seconds per side. Pick up bread ( use those handy tongs I love so much!) and let excess batter run off. Swirl some butter in a the skillet and add bread. Cook 1 minutes 45 seconds on the first side and about 1 minute on the second side. Serve immediately.