In Pozen the Minhag was, not to eat raisins (dried fruit) on Pesach except for the last day (Achron Shel Pesach) Reb Akiva Eiger asked his son in law the Chasam Sofer,What would the Din be, Achron Shel Pesach falls on Shabbos. Would it be permitted to cook on Sheviei Shel Pesach (using the raisins), for the following day?
The reason an Eiruv Tavshilin allows you to cook for the following day, is because unexpected guest might show up on that day, and you will actually end up cooking for that day (הואיל )
Reb Akiva Eiger held it would be O.K. to cook with the raisins on Sheveei Shel Pesach for the following day even though you can’t serve it to the guest, since you might have a Choleh She’ein Bo Sakana , which is quite common . They are permitted to eat raisins on Pesach. Therefore the principle of הואיל applies and you may cook with the raisins for the following day (Shabbos).
The Chasam Sofer argues and holds that you may not cook with the raisins. His argument is, it is true that to have a Choleh She’ein Bo Sakana is common , however to have a Choleh that needs to eat raisins is not common and therefore we cannot use the principle of הואיל .
Shu”t Chasam Sofer O.Ch. 79