Following on from the recent baguette question (what if the bread kneaders hands were dirty?) French fries cooked in a wire basket in a vat of vegetable oil used only for that purpose. In a diner with non kosher ingredients. Are the main obstacles here: the knife that cut the spuds, and the plate they are served on? If they give me a paper plate... then just the knife? If they tell me it is a single purpose knife. (Or why do I even want to be there? Did not convince the hevre to go to the nearby kosher eaterie.)

Following on from the recent baguette question (what if the bread kneaders hands were dirty?) French fries cooked in a wire basket in a vat of vegetable oil used only for that purpose. 

In a diner with non kosher ingredients, are the main obstacles here: the knife that cut the spuds, and the plate they are served on? If they give me a paper plate... then just the knife? If they tell me it is a single-purpose knife.