Peel the potato and slice into thick slices. Boil in salted water until tender. Drain well. Purée potato in a ricer or food mill. Measure 125 grams of puréed potato and combine with the milk. Chill until cold.
Place the potato mixture in a deep bowl and, using a wooden spoon, sequentially beat the egg, egg white, and cream into the mixture. Set aside until needed.
Using either a nonstick pan or a plain pan coated with clarified butter, heat the pan over medium high heat. Using 1 tablespoon portions of batter, make 3" diameter crêpes. Set aside in the warm oven.