First fillet the salmon trout and place the sections, including the head, in about one and a half liters of cold water. Add root vegetables, peels, spices and herbs and simmer under boiling for at least an hour. Then pass through a fine sieve. Peel and cut the carrot and celery into bite-sized pieces, as well as the leek. Add to the soup and cook again until the vegetables are cooked through. Then set aside the soup for now.
For the dough, knead the flour with the semolina of durum wheat, eggs, oil, salt, dill and match powder. Dill and matcha powder ensure an attractive green color. Knead until you get a smooth dough. Wrap it in parchment paper and let it rest in the refrigerator for at least an hour.
Roughly chop half of the fish fillet and process into a fine farce using a food processor. Add the garlic, a slice of crusty roast, egg, salt and pepper. Mix as short as possible so as not to overheat the dough. Cut the other half of the fillet into thin cubes and fold into the mixture along with the finely chopped dill, creamed spinach, lemon zest and cream fraîche.
Roll out the dough thinly without kneading it again. You can use a roller for this, or ideally a pasta machine.
Place the stuffing in a wide strip on the dough, leaving enough edge to be able to fold into the pockets later. Beat egg yolk and brush the edges with it. Then fold the dough lightly over the filling and roll. Use a wooden spoon with a round handle to separate the individual Maultaschen and close them with light pressure. Separate the individual Maultaschen with a knife or pastry.
Bring the soup to the boil again and let the dumplings boil in the boiling liquid for about eight to ten minutes. Then serve immediately.
You can find tips on buying fish sustainably on the WWF and Greenpeace websites.