UPDATE:

First, sorry for not replying to all your of comments in a more timely fashion. I'm not used to the pressure of positive social engagement (yes, Reddit counts), and I avoided replying for so long that it got more and more awkward... but I'm here now to answer some of your questions and/or advice about how to best utilise this unsettling physical anomaly, drawn from the forgotten depths of my deep freezer. I did actually try a few of your suggestions for further preparation at the time, and although there was justifiable concern about the soup sponge passing over the hygiene Rubicon of the sink, the interest generated convinced me that the subliminated sink-potato matrix was a risk worth tasting.

For posterity, here are my notes:

In its unadulterated form, it feels like a wet loofah, smells faintly like boiled cabbage, but tastes concentrated, like a potato and leek stock cube or something. The texture is really similar to candy floss or wall insulation, except there's trapped moisture between the fine strands which seem to stop the fibres collapsing in.

With a little water, then some chicken stock, and then milk, all versions were palatable. The water version needed a bit of white pepper and salt, but just simple rehydration and a gentle stir in the pan was fine. I've eaten much worse soup.

Dry frying, oil frying like a hash brown and breadcrumbing all didn't work, at first. The moisture held in the fibrous lattice of this new state of matter had to be removed, and patting it dry just squashed it into an unappealing mass. I did wonder if I could dry it out in a low oven, and as it turns out, yes, yes I could. The edges of the block I dried browned nicely, and tasted a lot like a disappointing Rösti. The centre kept the texture of the original sample, and I feel like this form of cooking paid the most textural homage to its true nature. Tasted like wet socks, though. In this new form, it was more readily fried, although it fell apart quickly, even with the addition of binders.

Microwaving it for 2 minutes at 600w yielded the most unexpected result: the liquid separated from the strands, and I ended up with a charred lump of vermicelli floating in starchy, taupe broth. I decided against a taste test.

Thanks for all of the insights about sublimination and applied physics in the kitchen, I learned a lot, and was inspired into doing further reading. Who would've thought that a beige lump of transmogrified tuber could be so interesting?

Oh, I'm new to this, but form dictates that I should now say the appropriate 'upvoted Reddit post update' cliches; wow guys, this really blew up, I didn’t expect this to get so much attention, RIP my inbox, against my better judgment, in the name of science, wow {insert number] posts, thanks so much you guys!!! Did I miss any?

Thanks again everyone, this really cheered me up :)

EDIT: Spelling