Kissel

I'm going to preface this post by admitting that I'm pretty stupid. Really stupid. Stoooopid actually. This is part two of my battle with Larousse Gastronomique and I seem to be pinned down on the floor again...
Kissel is a drink I remember getting as a treat for good behaviour when I was little, the texture mystified me and I always assumed this was one of those things that my grandma alone knew how to make and there wasn't really a recipe for. Larousse has it all, I almost fell out of my chair when I saw it and I knew there and then that I would do whatever it took to make it, I've been really good this year! This task was complicated by the fact that I can't read properly.
Here's the part of the recipe that I found most confusing: Mix 50g potato flour, cornflour or tapioca into the juice. I spent literally weeks hunting all of London for potato flour, I know I could have ordered in online, if I wanted a 5kg bag, but Internet shopping, there's nothing more satisfying than having the thing right there in your hand (and also all the Christmas present buying I've done made me a little apprehensive about using my credit card, ahem ahem). I finally found the stuff in Planet Organic, which I'm really beginning to hate. Every time I can't find an ingredient in a regular supermarket, it's always there. I don't know why this convenience annoys me, but it does. Bunch of stuck up bastards, who do they think they are!?
Don't mind me, I'm only lashing out because of my own inadequacies. When I finally got down to business it struck me that there is quite a big difference between the words or and and. Really, instead of running around, chasing after potato flour (and tapioca) wildly I could have been relaxing in my kitchen with my safe boring old box of corflour. So now I have a useless overabundance of starch in my kitchen, duh.
Result: I'm serving it in my Moomin mug to liven up something that is basically thickened fruit juice (I can't believe how excited I used to get over this, I guess I really am that stupid).
The book suggests serving it warm or cold, but I remember correctly, the proper way to drink this is as soon as it's made - scalding hot so it burns the roof of your mouth. And then you stick your finger in the cup so a skin forms around it. Yum!
The cranberries are still really sour, all the sugar does is take their tartness away, you can taste all the Vitamin C, as my brother puts is. It really takes me back :). Now all I have to do is figure out how much tapioca pudding I can get away with making...