Peri peri is a dried Bird's Eye Chili called Peli Peli by locals from South Africa but the settlers back then called it Peri Peri. It comes as a dried spice and could probably be sprinkled on your fries when done. It also comes as an ingredient in the form of sauces and comes in mild to super hot - used much like BBQ sauce or ketchup.
So, I would think that you would just make French fries and then sprinkle the dried spice on them that can readily be found online. I don't know where it falls on the Scoville Heat Unit but I assume it's up there.
Now - though probably a v. basic thing - could you tell me how to make great fries - I never know how thick to cut them - should they be thick or thin, and is there a way of making really nice and crispy on outside and soft inside WITHOUT re-frying - i hate that!
I like my fries on the thin side. I've never even tried to do thick ones. I cut my fries in about 1/4" strips. If you want yours larger just experiment with a few at the beginning on cooking time.
Heat Crisco shortening to 365° F in a saucepan. (make sure your saucepan is large enough to give you some room for boiling oil once the fries are put in and less chance of burning yourself). Cook 2-3 cups of potato strips at one time, adding slowly. Cook until potatoes are tender and lightly browned, about 10-15 minutes (for thin fries it might not even take 10 minutes). Drain potatoes on paper towel well.
While frying remaining potatoes, keep fried ones warm in oven set at low temperature. Salt or season as desired.