In a large saute pan, saute the sliced onion in the 2 tablespoons butter until lightly caramelized ( about 10 minutes over medium heat). Set aside. In a small sauce pan, heat the half and half to simmering and reduce by about 1/3. Add the salt, white pepper and nutmeg. Off the heat, stir in 1/2 cup of the cheese. In a well buttered baking dish ( I used a 9 x11 x2 inch oval), layer 1/3 of the potatoes, slightly overlapping. Layer 1/2 of the pears over the potatoes. Sprinkle the caramelized onions over the pear layer and then layer the second third of the potatoes followed by the rest of the pears. Layer the remaining potatoes over the top. Pour the cream and cheese mixture over the casserole followed by the remaining one cup of cheese. Bake, covered, at 350F for 1 1/2 hours. Uncover and continue to bake 15 to 20 minutes more.