Spray a 9 x 13 baking dish with cooking spray. Set aside.
In a large bowl, whisk together eggs, eggnog, sugar, nutmeg, cinnamon, salt and extract.
Add bread cubes, a large handful at a time, gently stirring in-between to coat evenly with the egg mixture.
Place in prepared baking dish. Cover and refrigerate overnight (8 hours) or a minimum of 20 minutes to allow bread to absorb custard.
Prepare the topping by stirring brown sugar, cinnamon and pecans in a small bowl to combine. Place in an airtight container to store (if refrigerating overnight). You'll use this right before placing the casserole in the oven.
When ready to bake, preheat your oven to 350 degrees F. Top casserole evenly with pecan topping.
Bake (uncovered) for 45 minutes, or until top is lightly browned and egg mixture is cooked.