Cut the escalopes at the edges, cover with transparent film and pound well. Season with salt and freshly ground black pepper. Cover escalopes with mustard and turn around in flour. Heat oil in a pan and fry escalopes on each side until lightly brown. Remove escalopes and set aside. Sautée tomato paste in the pan, douse with wine and boil down for some minutes. Add beef stock or the gravy and bring to the boil. Return escalopes, add the bay leaf and simmer covered by low heat for approx.50 minutes.
For garnish peel onion, half it and cut into fine slices. Cut gherkins into small, elongated pieces. Chop anchovy fillets. Melt butter in a small pot and sautée onion until translucent, add gherkins, anchovies, parsely and sautée some minutes more. Remove from the hotplate.
Blend thoroughly sour cream, flour and 1tsp.of water. Remove escalopes and keep warm. Bring sauce to the boil, stir in sour cream mixture and simmer for 5 minutes until smooth. Remove bay leaf and season to taste with salt and freshly ground black pepper.
Return escalopes and let them sit a little bit.