In a large mixing bowl, tear up leftover bread into 1-inch cubes.
In a separate mixing bowl, whisk together eggs, cinnamon, nutmeg, sugar, milk and vanilla extract. Add bread and apples and toss until coated. Mix in pecans.
Grease a 10-inch cast-iron pan with butter.
Add bread mixture.
Cover with foil and refrigerate overnight.
Preheat oven to 400 degrees.
Place casserole in oven and bake for 30 minutes or until bubbling and brown.
