Makes 5 to 10 servings. Refrigerate overnight.
Spray a 15x10-inch baking dish with nonstick cooking spray. In heavy saucepan over medium-low heat, melt butter with brown sugar and corn syrup, stirring until smooth; pour into baking dish. Place bread slices a atop the butter mixture. Whisk together eggs, half and half, vanilla, triple sec and salt. Pour over the bread and cover and refrigerate overnight. In the morning, preheat oven to 350 F, let French toast sit at room temp for 30 minutes, then bake for 30-35 minutes, then bake for 30-35 minutes. While french toast is baking, put teach slices in a bowl. Add white sugar and peach brandy; stir to combine. Place 1-2 pieces of French toast on each plate, brown sugar side up. Spoon peaches over the top of each serving.