Preheat oven to 350 degrees. Spray a 9x13 inch baking dish with vegetable cooking spray. Pierce potatoes and bake for 1 hour 15 minutes, until very soft. Peel baked potatoes; mash hot potatoes in a large bowl. Add cream cheese, butter, one cup of cheddar cheese and sour cream; mix well. Add garlic, salt and pepper; mix. place potatoes in prepared dish. (At this point, casserole can be covered with plastic wrap and refrigerated until ready to bake;) bake at 350 degrees for 30 to 35 minutes until hot. Sprinkle with remaining one cup of cheese on top. Return to oven for 5 minutes until cheese melts. Top with chives and bacon. Note: to make a fancy presentation, place potato mixture into an icing piping back fitted with a large star tip and pipe into baking dish. Bake as before.