From Longman Dictionary of Contemporary Englishthe icing on the cakethe icing on the cakeGOOD/EXCELLENTsomething that makes a very good experience even better It was a great day, but meeting her there was just the icing on the cake! → icing
Examples from the Corpus
the icing on the cake• Items such as these are the icing on the cake.• The prospects of a change in government banking policy has been the icing on the cake.• Female speaker It's an added bonus, the icing on the cake.• And for the family business with such humble beginnings the expansion is just the icing on the cake.• This is just the icing on the cake.• I would also endorse heartily our bikes, which provided the icing on the cake.• A year ago, Holiday Inn put the icing on the cake at two of its Florida properties.• And just to put the icing on the cake he has named it Black Forest Chateau. 