To make the marinade,
put all the marinade ingredients in a pan and bring
to the boil. Lower the heat and simmer gently for
20 to 30 minutes. Remove from the heat and allow to
cool completely.
Arrange the herring fillets
skin-side down in a flameproof roasting pan, pour
the marinade over them and slowly bring to the boil
on the hob. Immediately remove from the heat and
allow to cool.
To finish the dish, blanch the
carrot in boiling salted water for 2 to 3 minutes,
then refresh in cold water and drain.
Arrange the
cooled herring fillets on a serving plate and spoon
some of the marinade over them. Scatter the carrot
slices over the fish and arrange rings of onion
on
top.