Whisk the eggs, milk, cream, brown sugar, and vanilla until combined. Pour about a cup of the egg mixture into the bottom of a greased 9"x 13"x 2" baking pan.
Arrange the bread slices in the pan, laying them flat in the bottom of the pan. Pour the remaining egg mixture over the bread.
Cover and refrigerate 8 hours or overnight.
To make the topping:
Preheat oven to 350°F (175°C).
Place the butter, brown sugar, maple syrup, and salt in a small saucepan. Cook over medium heat, stirring frequently, until the sugar has dissolved and the mixture is smooth. Stir in the pecans.
Pour the topping over the chilled bread.
Bake 30 to 35 minutes, or until the bread is golden and a thin knife inserted into the egg mixture comes out clean.
Notes
*I used most of two small French baguettes, which are not as wide as store-bought French bread. If you do the same, you'll need more slices to fill the pan.