parmesan cheese (or whatever you have on hand)
Clean the potatoes and bake in preheated oven (350 degrees) for an hour. (you want to bake them just until a knife can slide thru them...try not to overbake) Remove them from the oven and slice lengthwise. Carefully scoop out the inside of the potatoes leaving about 1/4 of an inch still intact to the skin. Place all the scoopings in a bowl and add some butter, milk, garlic salt, pepper, cheese, and a dallop of sour cream. I don't do measurements with these ingredients so just add what you think. If you like other things in your potatoes, add those too....whatever you like! Mix until all smooth with a hand mixer and carefully scoop back into the potato skins. At this point you can place them in the fridge covered, and wait until you are ready to serve. About 30 minutes before serving, place them in the oven at 350 for about 30-40 minutes, or until warmed and browned. This also works well with red potatoes.