GHOTI

If GH can stand for P as in Hiccough
If OUGH can stand for O as in Dough
If PHTH can stand for T as in Phthisis
If EIGH can stand for A as in Neighbour
If TTE can stand for T as in Gazette
If EAU can stand for O as in Plateau
Then the right way to spell POTATO should be:

GHOUGHPHTHEIGHTTEEAU