Preheat the oven to 400° and have ready a large, greased au gratin pan.
Rinse and peel the potatoes. Using either a sharp knife or a mandoline, cut the potatoes in slices no thicker than an ⅛". Transfer to a medium-sized saucepan and pour over cream, salt and pepper. Stir and place over medium-high heat. Bring to a simmer.
Reduce heat to maintain a constant simmer, placing lid slightly ajar. Watch pot so that it does not boil over. Stir occasionally, and remove from the heat once the potatoes are fork tender, about 12 minutes.
In a small bowl, combine the two cheeses and mix together. Set aside until ready to use.
Using a skimmer or a slotted spoon, transfer half of the potatoes to the prepared pan, and sprinkle with half of the cheese. Do not discard of the cooking liquid. Add the remaining potatoes and sprinkle over the rest of the cheese. Pour the cream evenly over the potatoes and cover with aluminum foil.
If possible, transfer the prepared pan to a heavy duty baking sheet to keep any drippings from hitting the floor of your oven. Bake for 20 minutes. Remove the foil and bake for 10 minutes more, until golden and bubbly. Allow to cool for 10-15 minutes, serve and enjoy.