Praise be to Allah.
Flavourings in food products nowadays may be natural or they may be artificial.
The ruling on chicken-flavoured potato chips may be determined by referring to the ingredients listed on the packaging. If it states that the flavour is natural, which means that they used something derived from chicken, then in this case, based on how chickens are slaughtered in Western countries, it is not allowed to eat this product, because the basic principle concerning meat is that it is haraam unless it is known or well-established that it was slaughtered according to Islamic rules, as the fuqaha’ have stated.
An-Nawawi (may Allah have mercy on him) said:
There is an important principle, which is that if there is any doubt as to whether an animal was slaughtered in a manner that made it permissible to eat, it is not halaal, because the basic principle is that it is haraam [unless proven otherwise]. There is no difference of scholarly opinion concerning this.
End quote from Sharh Saheeh Muslim (13/78).
Al-Khattaabi (may Allah have mercy on him) said:
If the basic principle concerning a thing is that it is not allowed, and it is only regarded as permissible if it meets certain conditions and is done in a certain way – such as intimacy, which is only permissible after marriage; or such as mutton or lamb, which is only permissible if the animal is slaughtered in the prescribed manner – then whenever there is doubt as to whether these conditions have been met and fulfilled in a manner that makes it permissible, then they remain as they originally are, not allowed and haraam.
End quote from Ma‘aalim as-Sunan (3/57).
These meats may be deemed to be halaal, either by finding out that they were slaughtered in the prescribed manner, or because that is thought most likely to be the case, or because that is what customarily happens.
The prevailing custom in Western countries nowadays is that the slaughter of chickens is not done in the manner required by Islamic teaching. This is something that is well-established for the Muslims who reside in those countries. Hence they do not eat chicken except that which is labelled as having been slaughtered in the prescribed manner, or is labelled as “halaal”.
But if it is written on the packaging that the flavouring is artificial, then it is permissible to eat the chips in this case, because artificial flavouring is derived from something other than meat; it is taken from plants and other sources, and from artificial substances. The basic principle with regard to substances is that they are halaal and permissible, unless there is anything to indicate that they are haraam.
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
It should be understood that the basic principle with regard to all substances of various types is that they are halaal for humans in all cases, and that they are taahir (pure). It is not forbidden to handle them or touch them. This word is a comprehensive term and is general in meaning; this is very important and is of great benefit and an immense blessing.
This indicated by ten types of evidence – that I can think of – from shar‘i sources, namely: the Book of Allah; the Sunnah of His Messenger; following the way of the believers as referred to in the verses in the verses (interpretation of the meaning): “O you who have believed, obey Allah and obey the Messenger and those in authority among you” [an-Nisaa’ 4:59] and “Your ally is none but Allah and [therefore] His Messenger and those who have believed” [al-Maa’idah 5:55]; qiyaas (analogy); contemplation; ways of thinking and studying...
End quote from Majmoo‘ al-Fataawa (21/535).
And Allah knows best.