Lightly butter a 9" x 13" baking pan or similar-sized casserole dish. Slice a day-old baguette into 3/4" to 1" slices, and lay them in the pan; you'll need about 21 slices to fill the pan, making a single layer., In a medium-sized bowl beat the eggs, then whisk in the milk, sugar, vanilla, nutmeg and salt., Pour this mixture over the bread, and let it soak in while you're preparing the topping., Peel and slice the apples thinly. Toss them with the remaining topping ingredients, and spread them over the bread in the pan., Cover the pan, and refrigerate overnight; or for up to 48 hours., Remove the pan from the refrigerator, uncover it, and bake the French toast in a preheated 375°F oven for 45 to 55 minutes, until the apples are soft and the eggs set., Remove from the oven, and sprinkle with the sugar of your choice, if desired; or drizzle with maple syrup.