1. Peel the potatoes and slice as thinly as possible on a mandolin directly into a large, 8-quart container filled with 4 quarts of cold water. Cover and refrigerate overnight.
2. Drain the potatoes and rinse with clean, cold water, spin-dry in a salad spinner. Transfer the potatoes to an 11-quart pot, cover with the milk and set over medium heat. Bring to a simmer, about 35 minutes. Reduce the heat in order to maintain a simmer and cook, uncovered, until the potatoes are fork tender and beginning to fall apart, 25-30 minutes.
3. Reserve 1 cup of the cooking milk. Drain the potatoes thoroughly in a colander and return them to the pot. Press potatoes through a ricer into a large mixing bowl. Add the reserved hot milk, butter, white truffle olive oil and salt. Use an electric hand mixer to whip on low speed for 15 to 30 seconds. Do not over whip.