If using giblets, place giblets and 1 cup milk in medium bowl. Let stand at room temperature at least 15 minutes.
Meanwhile, preheat oven to 350 degrees F. Divide torn white bread between 2 rimmed baking pans. Transfer to oven and bake 12 to 15 minutes or until crisp. Set toasted bread aside; leave oven on at 350 degrees F.
Meanwhile, place eggs in large bowl and whisk until smooth. Add cubed stuffing, stock and remaining 1-1/4 cups milk; toss to combine.
Melt 8 tablespoons butter in small pot or microwave-safe dish.
Spray large casserole dish with cooking spray. If using giblets, proceed with Step 6 and then 8-9. If NOT using giblets, proceed with Steps 7-9.
If using giblets, remove giblets from milk; discard milk. Finely chop giblets. Heat remaining 2 tablespoons butter in large skillet over medium heat. Add chopped giblets and cook 3 minutes, stirring frequently. Add onion, celery and garlic; season with salt and pepper. Cook 5 to 7 minutes or until vegetables are softened, stirring occasionally. Add poultry seasoning and sage; cook 1 minute, stirring constantly.
If not using giblets, heat remaining 2 tablespoons butter in large skillet over medium heat. Add onion, celery and garlic; season with salt and pepper. Cook 5 to 7 minutes or until vegetables are softened, stirring occasionally. Add poultry seasoning and sage; cook 1 minute, stirring constantly.
Add toasted white bread, melted butter and onion mixture to bowl with cubed stuffing and milk. Stir for 1 minute or until toasted bread is very well moistened.
Transfer mixture to prepared baking dish and cover with foil. Transfer to oven and bake 30 minutes. Remove foil; bake 15 minutes longer or until the top of the stuffing is golden brown and the internal temperature reaches 165 degrees F.