Slice the Black Angus rump steak into thin strips, cutting against the grain to keep the meat tender.

Place the steak strips in a mixing bowl and season them with Maldon sea salt and black pepper.

Heat the large frying pan over high heat and add the olive oil.

Sear one-third of the seasoned steak strips for 1 minute, turning with tongs until browned.

Transfer the seared steak to a clean mixing bowl and repeat with the remaining steak in two more batches.

Add the unsalted butter to the same frying pan and melt it over medium-high heat.

Add the chopped onion and sauté, stirring, until softened and lightly golden, about 5 minutes.

Add the finely chopped garlic and sliced portobello mushrooms to the pan.

Cook the mushrooms, stirring occasionally, until softened and reduced in volume, about 8 minutes.

Season the mushroom mixture with Maldon sea salt and black pepper, then sprinkle in the all-purpose flour.

Stir the flour into the mushrooms until no dry flour remains and cook for 1 minute.

Return all seared steak strips and their resting juices to the frying pan.

Pour the brandy and Commandaria wine over the steak mixture, then carefully ignite the alcohol with a lighter.

Allow the flames to subside completely, keeping the pan uncovered and away from any flammable materials.

Pour in the beef stock and stir in the Dijon mustard.

Add the fresh thyme and bring the sauce to a gentle boil.

Simmer until the sauce thickens slightly and the steak is heated through, about 3 minutes.

Stir in half of the fresh parsley and all of the heavy cream.

Warm the creamy sauce gently for 1 minute without boiling vigorously, then remove the pan from the heat.

Serve the creamy steak and mushrooms hot, then sprinkle with the remaining fresh parsley.