If you're talking about a recent ad then I don't know, but if you're talking about one from the 70s or 80s which had a granny type woman with a thick scottish accent then it was Campbell's soup. They used to stand a spoon up in a tin whilst saying the phrase at the end of the advert.
It was DEFINITELY Barbara Mullen (Dr Finlay's Janet) in the Csmpbell's soup advert. The phrase is still used as a light hearted insult in Scotland when referring to a stupid (or "thick") statement by a friend :-)