Because I know I first attempted (and probably failed) pommes souffles in my mother's kitchen as a teenager I knew my source for the recipe had to predate the interwebs, and was almost certainly from either Mastering Vol. I or Vol. II or Joy of Cooking.
Turns out it was Joy of Cooking, not mastering. My assumption that it was Julia's recipe was because I remember it being incredibly thorough, discussing all the complicated nuance of making them-- even going so far as to include a short history on the origins of the dish (supposedly Louis XIV's chef in a panic).
So, after an hour of thinking I'd gone daft, (plus the frantic call to my mother), I strongly recommend that you (and other folks) try the recipe from Joy. It is helpful and detailed, and yet another reminder why "Mastering" and "Joy" remain the only "must have" cookbooks.