Make Ahead French Toast Casserole

Casserole:
1 (16 oz) loaf supermarket french bread sliced 1/2" thick
8 large eggs
2 cups whole milk
2 cups half and half
1 TBS sugar
2 tsp. vanilla extract
1/2 tsp cinnamon
1/2 tsp nutmeg

Topping:
1 1/2 sticks unsalted butter, softened
1 1/3 cup light brown sugar
3 TBS corn syrup
1 1/2 cups chopped pecans

Heat oven to 325 and arrange bread in single layer on 2 baking sheets. Bake until dry and lightly golden about 20 minutes, rotating baking sheets. Grease bottom and sides of a 9 by 13 baking pan with butter. Layer the prepared bread tightly in the pan (2 layers). Whisk together the eggs, milk. half and half, sugar, vanilla, cinnamon, and nutmeg and pour evenly over the bread. Press lightly on the bread to submerge. Cover with plastic wrap and chill 8-24 hours.
For topping: When ready to bake, adjust oven rack to middle and heat to 350. Mix the butter, brown sugar, and corn syrup together until smooth. Stir in pecans. Spoon topping over chilled casserole, spread in even layer. Place dish on rimmed baking sheet and bake until puffed and golden about 60 minutes. Cool 10 minutes before serving.
America's Test Kitchen Recipe.