Clean the fish fillet, sour with lemon juice and let stand for 10-15 minutes. Then cut into cubes and only season with salt before roasting. Dice the onion. Clean the mushrooms and cut into half slices.
Heat the oil in a saucepan and fry the onions in it. Add the mushrooms and fry them and then fry the fish (the fish last, because it disintegrates very quickly). Deglaze with vegetable stock. Mix the flour with a little water and bind the goulash with it. Season with soy sauce, pepper, paprika, curry and possibly a little salt.