Making "french fries" out of Cassava/Yuca root
This is how my mom prepares it (she's from Brazil, so it might be a tad different):


Cut off all the dark brown skin
Wash it and put it into a pot of water and bring to a boil
Boil for about 10 minutes (it should still be slightly firm, but not hard)
Cut it up into french-fry sized pieces 
Put the slices in a single layer on a cookie sheet and place in the freezer for about an hour
Heat oil, fry them for about 10 minutes (until golden brown)
Sprinkle with salt


Steps 1-5 can be done ahead of time and you just pull out what you need from the freezer to fry. I have not personally made these, but I ate hers a lot and they were fantastic!