Peel red bell peppers or cook them for 10 minutes in salted water and then cut into small cubes. Cut peeled potatoes and spring onions into cubes. Mix with red bell peppers and season with salt and pepper. Place vegetables in the middle of the baking paper and spread with a dash of white wine. Season trout fillets with salt and pepper. Place them upon the vegetables and spread butter flakes on it.
Brush the edges of the baking paper with egg white and fold to a parsel. Bake in the oven about 15 minutes at 160 °.