GMAT Sentence Correction (SC) | Re: Help needed on an idiom

sayantanc2k i searched a couple of places myself. nothing found.
As hot as to bun my mouth
So hot as to burn my mouth

PS, one veritas question states that 'So hot as to burn my mouth' is idiomatic. Question ID: 08379

I have found such usages also being a part of wrong answers. really confusednow.
carcass chetan2u Please guide on the above 2 usages.