Icing on the cake

tʃaɪniːzle̞tə tʃaɪniːzle̞tə tʃaɪniːzle̞tə tʃaɪniːzle̞tə keɪ aɪ ɛn dʒeɪ əʊmakɹɒn tiː iː ɛn keɪ eɪ

In Japanese 錦上添花 (kinjō tenka)

This is a direct borrowing from Chinese, meaning 'to add flowers to the brocade'.