Large fillet (350 g) cut lengthwise, not cutting to the end. Open it like a book and beat it back a little. I had 2 small fillets. I cut them up, beat them off slightly, and put them close together. Add salt and pepper to taste. You can add spices for meat.
Chop 100 g of fillet in a blender with half an egg and half an onion grated on a large grater. Add salt and chopped herbs and mix.
Put the minced meat on the edge of the beaten fillet.
Roll it up.
Grease the foil with oil. Lay out the roll. Wrap tightly. Then take another foil and roll the second layer, twisting the edges like candy.
In boiling water, lower the roll in foil. Cook for 30 minutes over moderate heat.
After 30 minutes, get the roll, cool.
You can fry in vegetable oil until a beautiful Golden brown, or you can leave as I have, a dietary option, without roasting. Cut and serve.