There are some foods served in restaurants in which a small percentage of alcohol was used during cooking or which include store-bought sauces containing a small amount of alcohol. Is it correct that this small quantity is burned off during cooking or not? And is this halal or haram? Please advise and may Allah reward you.

All praise is due to Allah and may peace and blessing be upon the Messenger of Allah, his family and companions. To proceed:

What must first be pointed out is that it is not permissible to use alcohol in cooking food, whether in small or large quantities, since there is no exigent need (daroorah) for that, nor is there any urgent necessity (hâjah mâsah) which would assume the status of exigent need. As such, this door should be closed for good in Muslim restaurants, for alcohol is mother of all foul, evil things. Ten categories of people were cursed in relation to it and he who drinks alcohol is not a believer while he is drinking it [references to hadith].

As for using food products which had some amount of alcohol used in their cooking, if this percentage has completely evaporated and not even the least trace of it remains, and the use of foods like this, neither in small nor large quantities, does not affect the mind of those who eat it, then the ruling might be that it is permissible according to consideration of the basic principle [that food is halal until proven haram]. However, uncertainty remains as to whether or not the traces of this alcohol have totally vanished, especially according to those who say that alcohol is impure and these are the greater percentage and the vast majority of scholars. As such, avoiding this is more prudent in terms of religious duty and more certain in terms of clearing the conscience.

And Allah Almighty is the Most High and He knows best.