From what I've read, heat doesn't actually kill the psilocybin...it just speeds up the oxidation process. So basically...heat doesn't hurt psilocybin anywhere NEAR as much as HEAT PLUS AIR (or hot air) does.
This is why you can't BOIL 'shroom tea, but you can heat it up to ALMOST boiling because the psilocybin can't oxidize in water that doesn't have oxygen passing through it.
I told my friend this and he is still insisting that "It'll be fine, I saw something on the internet about how you can do it as long as you keep the oven temp below 400*F...besides, shouldn't we be fine as long as we eat the brownies shortly after we take them out of the oven?". Of course, I replied, "Sure, if the psilocybin isn't gone by then!"
If he absolutely MUST cook the shrooms, should we make thick, fudgy brownies, so they won't be porous with lots of oxidizing air in them?