if you can find some cheap herring, this is a great way to preserve them as a treat. when i was a fishmonger i would make these by the hundred, selling them at £1 each and making a tidy profit!
for 10 rollmops:
5 herring, scaled and filleted.
make a strong brine and soak the fillets for an hour or so. once soaked rinse them off and check for pin bones.
a small onion and a couple of pickled gherkins, finely sliced.
roll up a fillet stuffed with a bit of onion and a slice of gherkin, spear with a toothpick to hold them rolled.
put these to one side whilst you make the marinade.
for the marinade:
1 cup each of:
white wine vinegar
pickling condiment
dry cider.
and half a cup of a good balsamic.
add bay leaf (i used 3) a couple of heaped teaspoons of brown sugar and a shake of mustard seeds and some peppercorns (i like the mixed ones they're more fruity!)
reduce the marinade by about 20%. adjust the flavour now, taste it and add sugar or whatever you think it needs to bring it in.
let the marinade cool.
layer the rollmops with onion and some more gherkin in a sterile jar.
pour your delicious marinade over the rollmops to cover.
then chill.
i tend to put them in the warm marinade but you dont need to, i reckon the marinade soaks in better whilst its still warm.
you can eat them after 5 or so days, and they should keep in the fridge for a few weeks.
enjoy!