Clean the fish and cut into cubes. Blanche (drop the cabbage leaves into boiling salted water for about a minute) then remove and drop into iced water and drain. You can remove some of the stalk if you wish but make sure you do not separate each leaf. Separate your butter into 3 X 50 grams. Chill one amount ready for sauce, it needs to be very cold .
brush the mushrooms and chop roughly, fry in 50 grams of unchilled butter ,remove from pan,mix with fish.( if using prawns add raw to the mushrooms. mix well just before rolling the parcel. They will cook in oven adjust time to 20 minutes) Season with salt ,pepper and a little Cayenne pepper.Add a little mixture to cabbage leaf (two leaves for one roll) and make a little parcel. Fry in 50 grams of unchilled butter carefully for about a minute from all sides. Chill rest of the butter
Transfer to ovenproof dish, pour over the frying butter and cook at 200C for 15 minutes in oven.
Finely chop the onion and cook in the red wine ,reduce until half the liquid.whisk the very cold butter under. Season with salt and pepper.Serve with new potatoes or fried potatoes and and the sauce
If you are not happy to use red wine, then use a pomegranate or cranberry juice . If you want a deeper colour for contrast add drop of red food colour.