Preheat oven to 375° F. Remove butter and cream cheese from refrigerator to allow to come to room temperature while potatoes bake.
Prick each potato a few times each with a fork. Rub the outside of each potato with a small amount of oil. Place potatoes directly on oven rack and bake until soft when pressed, about an hour or so. Remove from oven and cool until you can comfortably hold them in your hands. ***Note*** You could microwave potatoes to speed up process.
Place cream cheese and butter into mixing bowl. Slice each potato in half lengthwise then gently scoop out the potato into the bowl, leaving a thin potato shell (place shells on baking sheet as you go). (Note: put the cream cheese and butter in first, the heat from the hot potatoes will soften it while scooping it into the bowl). Add sour cream, milk, salt and pepper to taste, mixing together until smooth and creamy.
Scoop the mixture back into the potato shells. Top with cheese and country ham. Bake until cheese is melted and potatoes are heated through, about 15-20 minutes. Garnish with chopped green onions or chives and serve immediately.