My question is,
It comes out that according to Tosafos, the Chiddush is that Basar which was soaked with Cholov for 24 hours is muttar to eat. This Chiddush is in fact a leniency that does not appear in other forbidden foods (Tosafos HaRosh). If this is the case, what is the p'shat: MiBasar beCholov mai taima delo gamrinan, deChidush hu! Since the Chiddush is a leniency in Basar beCholov, (whereta-am ke-ikar is de-oraisa) then by shaar issurim (where there is no such leniency of soaking hetter with issur for 24 hours) kal vechomer ta-am ke-ikar will be de-oraisa, i.e. you can surely learn sha-ar issurim from Basar beCholov.
Shimon Cobersy, London, England
We see from the fact that soaking -- which definitely gives Ta'am -- is still Mutar, that the underlying reasoning behind Basar b'Chalav is not Ta'am k'Ikar in it's classic sense, but rather it is a Chidush of the Torah from which we cannot learn to any other categories of Halachah.
Does this mean that by shaar issurim we say ta'am ke-ikar is de-oraisa but that
it is not learned from basar be-chalav, rather from somewhere else (as he indicates
in "Amar Rava - that Rava is a dichui be-alma)?
Yes, that is correct.