- Prepare the caramel base: In a small saucepan over medium heat, melt the butter, then add brown sugar and maple syrup. Stir until sugar dissolves completely (about 3-4 minutes). Pour this mixture evenly across the bottom of a greased 9×13 baking dish. 
- Arrange the bread: Place the bread slices in a single layer over the caramel mixture, slightly overlapping if necessary to fit all pieces. 
- Make the custard mixture: In a large bowl, whisk together eggs, half-and-half, vanilla extract, cinnamon, nutmeg, and salt until completely combined and slightly frothy. 
- Pour custard over bread: Slowly and evenly pour the egg mixture over the bread slices, making sure all pieces get soaked. Press down gently on the bread to help absorption. 
- Cover and refrigerate: Tightly cover the baking dish with plastic wrap and refrigerate for at least 8 hours or overnight (up to 24 hours). This resting time is crucial for the bread to fully absorb the custard. 
- Preheat before baking: When ready to bake, remove the dish from the refrigerator and let it sit at room temperature while you preheat the oven to 350°F (175°C). 
- Bake to perfection: Uncover the dish and bake for 40-45 minutes until the top is golden brown and the center is set (not jiggly). If the top browns too quickly, loosely cover with foil for the remaining baking time. 
- Rest before serving: Allow the French toast to rest for 5-10 minutes before serving. This helps the caramel set slightly and makes serving easier. 
- Serve with style: Serve warm, spooning some of the caramel sauce from the bottom of the dish over each portion. Garnish with fresh berries and a dusting of powdered sugar if desired.