Preheat the oven to 375℉. Adjust the oven rack to the middle of the oven.
Wash the potatoes and dry them.
Rub each potato with the olive oil and pierce each potato two or three times with a fork.
Place the potatoes each directly on the rack in the preheated oven.
Bake for 45 minutes to an hour. Before removing the potatoes from the oven, check the potatoes by piercing with a knife to make sure the potatoes are soft and completely cooked.
Carefully remove the potatoes from the oven and let them cool long enough to be able to handle - about 10 minutes.
Turn the oven up to 400℉. (If you are making the potatoes a day ahead, then you can turn the oven off.)
Horizontally cut the top off of each potato (about ¼ inch off the top). Cut just enough to end up with an opening just large enough to remove the cooked potato.
With a small spoon, gently remove the potato from inside each potato shell leaving about ¼ inch of a potato wall. Try not to break or tear the shell. Place the potato insides into the bowl of a standing mixer or another large bowl. Place each potato shell on a baking sheet.
Add the goat cheese, cream cheese, 6 Tablespoons of butter, half and half, salt and pepper to the warm potato.
Using a stand mixer, hand mixer or a potato masher, mash (or whip) the potatoes and other ingredients until combined and fairly smooth.
Remove about 2 ½ cups of the potato mixture and set aside. (Proceed with this step only if you are using a decorative tip to add potato to the top of the filled potato skins. Otherwise proceed to the next step and fill each shell.)
To the remaining potato in the larger mixing bowl, add the scallions and mix with a spoon to combine.
Add about ½ cup of the scallion potato mixture to each potato shell until the bowl is empty.
Fill a pastry bag with the potato mixture in the medium bowl. Add a large decorative tip and top the potatoes.
Lightly drizzle the last 2 Tablespoons of butter onto the tops of each potato and sprinkle each with the parmesan cheese.
Bake at 400℉ for 20 minutes until tops of the potatoes are lightly golden and the potatoes are completely heated through.