Preheat Oven and Prepare Pan: Preheat your oven to 375°F (190°C). Grease a large sheet pan with butter.
Arrange Bread: Arrange the bread slices in a single layer on the sheet pan. It's okay if they overlap slightly.
Make the Custard Mixture: In a large mixing bowl, whisk together the eggs, milk, cream, vanilla extract, cinnamon, nutmeg, and a pinch of salt.
Soak the Bread: Pour the custard mixture evenly over the bread slices. Make sure each piece is well coated. Allow the bread to soak for a few minutes, turning once to ensure both sides absorb the custard.
Make Topping: Mix together brown sugar, pecans, flour and salt in a bowl. Grate the cold butter into the bowl and mix until blended and crumbly.
Add Topping: Evenly sprinkle the pecan topping over the soaked bread pieces until covered.
Bake: Place the sheet pan in the preheated oven. Bake for 25-30 minutes, or until the bread is golden brown and the custard is set.
Serve: Remove from the oven and let it cool slightly. Cut into squares and serve with maple syrup, fresh berries, and a dusting of powdered sugar.