How to Make the Most Delicious Potato Casserole You've Ever Tasted

–4 large baking potatoes (about 2 ½ pounds)

–1 ½ teaspoons kosher salt

–¼ teaspoon pepper

–4 tablespoons butter, melted

–1 ½ cups shredded cheddar cheese, divided

–½ cup milk, warmed

–½ cup sour cream

–6 green onions, finely chopped and divided

–4 strips of cooked bacon, crumbled