Beat the beef schnitzel thinly, season with salt and pepper, and brush with tarragon mustard.
Sear the schnitzel on both sides in the Kelomat.
Remove the schnitzel from the Kelomat and fry the chopped onion and the pressed garlic. Pour water on top (be careful not to use too little water in the pressure cooker).
Close the Kelomat and "let it rise" once until the pressure relief valve comes out. Let the kettle cool down (if you are in a hurry, hold the kettle under cold running water, but I recommend reading the instructions for use of the pressure cooker).
Release the pressure from the boiler, open it. Put the schnitzel in the pot, pour water and a soup cube on top (if you have a stock you use this), add 3 teaspoons of tarragon mustard and a shot of "vinegar water" from the pickle jar.
Let the pressure valve "rise" twice or three times (depending on the thickness of the meat), that is to say, boil the whole thing twice or three times. Before "rising" for the second time, add a finely chopped pickle, season with salt and pepper to taste and season with a little acid (pickle water or Hesperides vinegar).
If necessary, thicken with a "flour dough". Alternatively, more onions give it enough consistency.