Brownie undercooked - can it go back into the oven once its cooled?

[prepperpig]

Its delicious but completely undercooked since I used a deeper tin than usual and didn't give it enough extra time. I made it last night. Can I pop it back in the oven for another 15 minutes or will it go hard and horrible?

I'd just eat it with icecream as it is and call it pudding!

It is really delicious but then I like eating the cake mixture. DH won't eat it like this (although the DCS will!)