A couple of notes referring to Japanese ingredient (4)
I believe the answer is:
miso
'referring to japanese ingredient' is the definition.
I can't tell whether this definition defines the answer.
'a couple of notes' is the wordplay.
'a couple of notes' means two substitutions for 'note'.
'note' becomes 'mi' (as in do-re-mi).
'note' becomes 'so' (musical note).
'mi'+'so'='MISO'
Can you help me to learn more?
(Other definitions for miso that I've seen before include "Soya-beam paste" , "Thick paste used in Japanese soups and sauces" , "Soya bean paste" .)