I know I love Poutine, the cheese curds are extremely mild tasting, both covered with a very flavourful Gravy. But somehow "popcorn" sort of ruins it for me. Plus, to my way of thinking, the Cheddar is too strong in taste for the fries. JMHO
I'm curious as to how you propose to combine a white cheddar flavour with your fries?
Have you been able to purchase this 'powder' (or what ever it is)?
Do you intend to just sprinkle it on? if it is a powder?
I'm pretty sure that there is a way to make fries from mashed potatoes. I have no idea what has to be done to them. But, I have seen fries being made at greasy spoon that were pushed out of a thing that I assumed was cutting a whole large potato into sticks for fries, all at once. But, I remember one day, the "sticks" that came out of that thing were over a foot long and the ends were raggy looking, not like the edge of a potato. So, I think it was extruding potato mush, not cutting whole potatoes.