• Preheat oven to 375°F. Coat a 9 x 13-inch baking dish with nonstick cooking spray.
• Scrub the potatoes and pierce each one several times with a sharp knife. Place them on a baking sheet and bake for 45 minutes or until they are soft in the center when pierced. Remove from the oven and allow to cool until they can be easily handled, then chop into bite-size pieces and transfer them to a large mixing bowl.
• In a separate bowl, whisk together the sour cream, milk, garlic, seasoning salt, and black pepper. Pour the mixture over the potatoes and add about ⅔ of the crumbled bacon, ½ of the green onions, and 1¼ cups cheese. Use a large spoon to toss until the potatoes are completely coated with the sour cream mixture. If the mixture seems too dry, you can add additional milk, in small amounts, for a creamier texture.
• Transfer to the prepared baking dish. Top with remaining cheese and crumbled bacon.
• Cover the dish with foil and bake for 30 minutes. Remove the foil and cook for an additional 5 to 10 minutes, until the cheese is melted and bubbly. Garnish with remaining green onions and serve.

Make-Ahead Instructions

• Assemble the casserole up to a day in advance, cover tightly with foil, and refrigerate. Let it sit at room temperature for about 30 minutes before baking as directed. Baking time may need to be longer if the dish is cold when going in the oven.