Whisk together the eggs, buttermilk, vanilla, cinnamon, nutmeg, and salt in a medium bowl; set aside.
Place the bread in a shallow baking dish large enough to hold the bread slices in a single layer. Pour the egg mixture over the bread; soak 10 minutes. Turn the slices over; soak 10 minutes more, or until soaked through.
Preheat the oven to 250°F. Place a wire rack on a baking sheet; set aside. Heat 1 tablespoon butter and 1 tablespoon vegetable oil in a large skillet over medium heat. Fry half the bread slices until golden brown, 2 to 3 minutes per side. Transfer to the wire rack; place in the oven while cooking the remaining bread. Wipe out the skillet; repeat with the remaining butter, oil, and bread. Serve warm with maple syrup, if desired.
