Preheat oven to 350 degrees. Wash, oil, salt and pierce the potatoes and place on a baking pan (or straight on oven rack).
Bake the potatoes for 1 hour and 15 minutes, until very soft.
Peel and mash the potatoes in a large bowl with a potato masher.
Add the cream cheese, butter, 1 cup of the cheddar cheese and the sour cream.
Stir well. Add the garlic, salt and pepper and stir again.
Spray 9x13 baking dish with cooking spray. Place the mashed potatoes in the dish.
Note: The casserole can be covered with plastic wrap and refrigerated until ready to bake.
When ready to bake, preheat oven to 350 degrees.
Remove the plastic wrap and bake the casserole for 30-35 minutes, until hot.
Sprinkle the remaining 1 cup of cheddar cheese over the top of the casserole and return to the oven for about 5 minutes, until the cheese melts.
Garnish with the chopped chives and crumbled bacon before serving.