Preheat oven to 350 degrees Wash and scrub all potatoes well, put them on a baking sheet and pop them into the oven. Cut a portion of the top off the head of garlic, far enough down to expose the garlic cloves. Place bulb in aluminum foil and drizzle with olive oil. Wrap tightly and bake in 350 degree oven with potatoes. In an hour, remove and cool the head of garlic. Check potatoes for softness. The potatoes should be VERY soft. If they are, pull them out,** if not ** bake until very soft. ** When garlic is cooled squeeze out all the roasted garlic cloves to a bowl - Set aside. When potatoes are done, remove and cool until they are able to be handled. Cut potatoes lengthwise and scoop out all potato pulp into a large bowl. Set potato skins aside. Continue until all potato pulp is in bowl. I like to finely chop up a portion of the skins and add to the potatoes. If you dont like skins, throw them away. Take the roasted garlic and mash with a fork, add to potatoes. Add about a cube of butter in chunks, and some of the sour cream. Using a potato masher start mashing up the potatoes until JUST mixed. DO NOT OVER MIX. Continue adding sour cream and butter until you get the proper consistency. Add seasonings of your choice, salt, pepper, seasoned salt, etc... Fold in the chunks of cheddar cheese. Put into sprayed casserole dish, cool completely and then cover with plastic wrap and refrigerate overnight if making ahead, or simply bake and serve! If making ahead, next day preheat oven to 350. Bring potatoes to room temp from refrigerator. Remove plastic wrap and cover with foil. Bake for 20 minutes, uncover and cook another 10 minutes. You can top with chopped chives, green onions or bacon bits if you wish......