Despite being now claimed by the belgians, the french fries are indeed a parisian recipe of the late XVIIIth century. Doughnuts sellers around the Pont Neuf first had the idea to use potato chips in their frying oil, before cutting potatoes into a stick shape. Then a belgian learned the recipe in mid XIXth century and brought it back to belgium where he sold "fried potatoes in Paris fashion".
[End of patriotic digression]
[End of patriotic digression]