I was reading about brewing the other day and was interested to discover the concept of the amylase rest (see this page on Wikipedia). Before the yeast is added to the mash, there's a stage where the mixture of water and malt is held at around 70C to allow the amylase enzymes to have a party. It's their favourite temperature, and so they quickly break down the starch molecules into smaller, sugar molecules, which the yeast can then turn into alcohol and CO2.
This seems like a good idea. I've already used autolysation, where you let the mixed dough rest before you knead it, but that was at about 40C at best. You can't go much higher because you'd kill the yeast. So what happens if you mix flour and water, bring it up to 70C and hold it there for a while?
(I mixed 200g of strong white flour with 200g of water at 70C, and then put this in a bowl over an saucepan of hot water on a low gas. The temperature of the mix initially fell, of course, but rose to nearly 70 before I turned off the gas and let it stand for 20 minutes. I'd expected it to be longer, but it was obvious that big effects had already happened. )
The short answer is that you get porridge. The texture of the dough is distinctly different from usual, and it's noticeably sweeter, which is what we want. So I added about 170g more flour, 100g water and half a teaspoon of dried yeast, and 3g salt. Kneaded this all together then let it rise. It didn't rise well, but looked ready for baking so I formed it into a pain d'epi shape and baked at 240 for 45 minutes.
Readers, it was a disaster. Doughy on the inside, but crisp of crust (all that sugar!) it was inedible for humans. Now I know why I've never seen this technique mentioned. Something crucial to the structure of bread is lost. The shivering ducks in Ladywell Fields loved it though.