Start by cutting the beef into cubes.
In a large pan over medium to low heat add the unsalted butter, a drizzle of vegetable oil and stir until the butter melts completely.
Add the meat cubes we cut earlier, the pickled cucumber juice and sauté everything very well until the water has almost completely evaporated.
Remove all the meat from the pan, add the onion cut into round slices, the crushed garlic cloves and sauté until the onion wilts.
Add the pickled cucumbers cut into smaller pieces and sauté for another 3 minutes.
Then, add all the meat again.
Season with the salt, a pinch of black pepper, the sweet paprika, the soy sauce, the mustard and stir to combine.
Now, dissolve the cornstarch in the water, add it to the pan and stir very well.
Finally, add green onions, parsley to taste and mix.
Serve.