Twice Baked Potatoe Casserole

5 pounds all-purpose potatoes, peeled and quartered
1/2 stick (4 Tablespoons) butter
1 1/2 cups shredded reduced-fat cheddar cheese, divided
1 cup 1% low-fat milk
1 cup reduced fat sour cream
2 eggs
1 cup sliced scallions
4 slices bacon, cooked crisp
2 1/2 teaspoons salt
1/2 teaspoon ground black pepper

Preheat oven to 350 degrees. Lightly coat a shallow 3 quart baking dish with non-stick cooking spray. Cook potatoes in a large pot with water to cover for 20 to 25 minutes, until tender when pierced. Drain well and return to pot. While potatoes are still hot, add butter and mash with a potato masher until smooth. Stir in 1 1/4 cup of cheese, milk, sour cream and eggs until blended. Then add 3/4 cup of scallions, 2 slices of bacon, crumbled; salt and pepper. Spoon into the prepared baking dish. Sprinkle with remaining 1/4 cup cheese and 2 slices of bacon, crumbled. Bake uncovered for 40 minutes or until the top is lightly golden brown. Sprinkle with remaining 1/4 cup scallions.