Preheat oven to 350 degrees then coat a baking sheet with cooking spray. Scrub each potato completely clean, rinse and pat dry. Pierce each potato several times with the tip of a knife or a fork and place on prepared baking dish. Bake 1 hour or until potatoes are cooked through. Remove from oven and set aside to cool.
While the potatoes cool, place a skillet over medium-low heat then fry bacon for about 10–15 until crisp but not dry. Transfer from skillet to a paper towel-lined plate to drain and cool. When bacon is cool, chop into small bits then set aside.
Once potatoes have cooled to room temperature or are slightly warm, the skins should be very easy to remove. If your family likes the skins, you can leave them on.
Cut potatoes into ½" pieces and place in a large bowl along with about half of the green onions.
In a separate small bowl, stir together the sour cream, mayo, milk, salt, pepper and garlic powder. Pour dressing over potatoes and stir gently to combine. Season to taste with salt and pepper.
Transfer into a 9" x 13" casserole dish. Spread into an even layer and sprinkle with shredded cheddar cheese, crumbled bacon and remainder of the green onion. Serve lightly chilled, room temperature or slightly warm.
One Last Thing
If you like a little heat, add diced green chiles or jalapeños to the top!