Webshield - how do I check SITE certificate chain

Using Chrome I click on the padlock to check the site certificate but all I can see is an Avast Certificate.

I am advised by security specialists (I am also experienced in security) to check the original site certificate chain so I can verify it is a trusted site. this being blocked. I understand the reason why it is replaced (so the data stream can be scanned). I have implemented similar boundary protection devices myself.

My serious problem is that I have no way of checking the ORIGINAL site security certificate. I can only see Avast’s assertion that it has been checked. THIS IS NOT ACCEPTABLE. Please enable me to check for myself the original certificate chain.