For a 4-to-6-cup soufflé mold or straight-sided baking dish 8 inches across, serving 4. You can bake this in a 4-cup mold with a paper collar, into which the soufflé will puff 2 to 3 inches over the rim and hold its puff when the collar is removed. Or bake it in a 6-cup mold, which will give you a more stable soufflé but less puff.