Preheat the oven to 400 degrees. Wash the potatoes, prick them with the tines of a fork and place them in the oven for about one hour or until tender. When the potatoes are cooked and cool enough to handle, slice them in half lengthwise and scoop the flesh into a bowl. Add the butter and cream cheese and mash into the potatoes. Heat the olive oil in a sauté pan over medium heat. Add the scallions, garlic and spinach and cook for 2-3 minutes until the spinach has wilted. Press the spinach to discard as much liquid as possible. Chop the spinach and fold into the potatoes. Mix in enough of the milk to achieve a moist and tender consistency. Season to taste with salt and pepper. Spoon the mixture back in equal amounts inside the potato skins. Sprinkle the tops with paprika. When ready to bake, preheat the oven to 375 degrees. Place the filled potato skins on a cookie sheet and bake for 10-15 minutes or until hot, with the skins crispy.