The oiliness of sardines is a perfect match with a tangy, sweet mustard sauce. In Scandinavia it's common to pickle fish like this, but in this country we don't seem to do it very often, which is a shame.
16 sardines, butterfly filleted and the heads and bones removed (marinated for 4-5 days)
For the marinade
300ml white wine vinegar
300ml warm water
2tsp sea salt
1tsp fennel seeds
8 juniper berries
2 bay leaves
6 shallots, peeled and cut into rings
For the sauce
2tbsp good-quality mayonnaise
2tsp Tewkesbury mustard
1tbsp clear honey
1-2tbsp chopped dill or fennel tops
Bring all of the ingredients for the marinade to the boil, then leave to cool and add the shallots.
Mix with the sardine fillets, then lay the fillets in a non-reactive container and pour over any remaining marinade.
Leave to marinate in the fridge for at least 4-5 days before serving.
To make the sauce, mix the mustard, mayonnaise and the honey, then whisk in a tablespoon of the marinade to about the consistency of double cream; stir in the dill.
To serve, remove the fillets and dry on some kitchen paper.
Fold them in half or roll them up with the skin on the outside and arrange on a serving plate with a few of the shallots on top and serve the sauce separately or poured over.