Prepare the rest of the ingredients.

Heat a large skillet over high heat and add 1/4 cup of the cooking oil. Add the marinated beef and let it sit undisturbed for about 2 minutes so it browns. Break it up with a spatula and cook for another 3 minutes until the meat develops good caramelization. Remove the beef from the skillet whilst keeping its juice and oil in the pan and set beef aside.

Add the chopped onion, garlic, celery, bell pepper and a pinch of salt. Sauté for about 4 minutes until softened.

Push the vegetables slightly to the side of the pan. Add the tomato paste, ketchup, Worcestershire sauce, yellow mustard, mushroom powder, red wine vinegar, fish sauce and pickle brine directly into the oil and cook for about 1 minute while stirring so the mixture caramelizes.

Return the beef to the skillet and mix everything together.

Pour in the beef broth and bring the mixture to a boil.

Reduce heat to low and simmer for about 30 minutes, stirring occasionally.

Increase the heat to medium high and cook for another 8-10 minutes so the sauce reduces further and becomes thick and glossy, coating the meat.

Add the unsalted butter and mix it into the beef until it melts.

Lightly toast brioche buns in. Fill with sloppy joe mixture and top with pickles or shredded cabbage or both.

Serve immediately.