Pickling fish is a common technique in Scandinavian. Originally conceived to preserve the fish, it is now used to add flavour and sharpness.

1. Mix the white wine vinegar, water, sugar, peppercorns and salt in a saucepan and place over a medium heat.

2. Bring to the boil then remove the pan from the heat and allow to cool to room temperature.

3. Place the fillets flesh-side down in a single layer in a dish, add thinly sliced carrot and onion rings and cover with the pickling liquid.

4. Refrigerate for 1 h then remove the mackerel and pat dry. When removed from the pickling liquid, the mackerel can be kept in the fridge for up to 2 days.

Enjoy!