Preheat the oven to 400 degrees.
Scrub the potatoes well and rinse under cool running water. Pat dry with a paper towel and prick the potatoes in several places with a fork. Place the potatoes in the oven and bake for 1 hour to 1 hour and 15 minutes, or until tender. Remove, from oven and set aside on a wire rack until cool enough to handle.
When the potatoes have cooled, cut each potato in half and, using a spoon or a melon baller, scoop the flesh out of the skin, leaving as little flesh as possible. Place the potato flesh in a large bowl and add 1 stick butter, the sour cream, heavy cream, salt and pepper and mash until chunky- smooth. Add the bacon, cubed white cheese, half of the grated cheddar, the green onions, and eggs and mix thoroughly.
Butter a 9X13 inch casserole dish with the remaining tablespoon of butter and reduce the oven temperature to 375.
Place the seasoned potato mixture in the prepared casserole dish and top with the remaining grated Cheddar cheese. Bake for 35 to 45 minutes, or until bubbly around the edges and heated through and the cheese is melted and lightly golden. Serve hot.