For the dough
Place the flour, salt, egg, oil and some water in a bowl.
Knead into a smooth dough.
Cover and let rest until the filling is ready.
For the filling
To make the filling, fry the bacon in the clarified butter then add the onion and the sauerkraut and mix well.
Add the spices and the white wine and simmer for approx. 10 minutes. Set aside.
Heat the butter and fry the mushrooms, season and add the thyme leaves. Add the sauerkraut from the previous mixture with as little liquid as possible and mix with the mushrooms in a bowl.
Roll out the dough thinly on a floured surface and cut out circles approx. 7-8 cm in diameter.
Brush the edges with egg white.
Boil some water in another pot.
Place a tsp of the filling in the middle of each circle.
Then fold in half and carefully press the edges together. Be careful that the filling does not leak out!
Cook the pierogi in the boiled, salted water.
Stir carefully when they rise to the surface and then cook for a further 2-3 minutes.
For the garnish
To make the garnish, brown the onion in a little clarified butter. Melt the butter in a large pan and quickly fry the pierogi. Sprinkle with the fried onion and garnish with thyme leaves.