Preheat the oven to 400 degrees F. Butter a 2-quart casserole and set aside. (As an optional tasty base, butter the bottom and sides of the pan liberally with the optional tablespoon of butter and sprinkle the Parmesan cheese evenly over the butter, coating the sides and the bottom of the pan.)
Place the peeled and chopped potatoes in a large pot and add an inch of water. Bring to a simmer, cover, and steam until the potatoes are very tender. This will take 15-20 minutes depending on the size of your potatoes pieces and the precise level of heat. Drain very well and return to the pot.
While the potatoes are cooking, mash together the 6 tablespoons softened butter and the cream cheese. Stir in the eggs, one at a time, followed by the salt and pepper.
When the potatoes are cooked and drained, add the milk and mash well. Add the egg mixture, stirring until incorporated and any lumps are mashed.
Transfer to the prepared baking dish. (At this point you may cover and refrigerate until ready to cook.) Bake until just set in the center and slightly golden on top, about 25-25 minutes, depending on the width of your casserole dish. The potatoes should be golden on top and almost firm with just a little jiggle to them. If potatoes have been refrigerated, add 5-10 minutes to the baking time. Avoid overcooking so as not to dry out the potatoes. If the potatoes are sufficiently brown on top but still very jiggly, cover loosely with foil.
Leftover potatoes are delicious. Gently reheat in the microwave or cover and warm in a low oven.
