Scrub mussels and pull out hairy beards. Rinse well and drain.
Place mussels,250 millilitres of the wine and bay leaves in a wide,heavy-based saucepan. Cover and cook over medium heat,shaking the pan occasionally,for 5 minutes,or just until mussels begin to open.
As soon as they open,remove from the pan and place in a colander set over a bowl. Allow to cool,removing mussels from their shells and reserving cooking liquid for another dish such as soup or risotto.
To make escabeche,heat oil in a heavy-based saucepan over medium heat. Add onion,garlic and a pinch of salt and cook for 5 minutes,or until the onion is lightly coloured. Add vinegar,paprika,peppercorns and remaining wine,then bring to the boil over high heat. Reduce heat and simmer for 8 minutes,then remove from heat and leave to cool for 10 minutes.
Stir mussels into escabeche and pour into a shallow dish. Leave to cool,then cover and refrigerate overnight. Serve chilled.