Parboil the potatoes for maximum crispiness: Place cubed baby gold potatoes into a medium pot, cover with cold salted water, and bring to a boil. Simmer gently for 5 to 6 minutes until just fork-tender on the exterior but still firm in the center. Drain thoroughly and let steam dry on a paper towel for 3 minutes.

Crisp the potatoes in cast iron: Heat 2 tablespoons olive oil in a large 12-inch cast-iron skillet over medium-high heat. Add the parboiled potatoes in an even layer. Sear undisturbed for 4 to 5 minutes until deep golden-brown, then toss and cook for another 3 to 4 minutes until crispy and fork-tender throughout. Transfer the potatoes to a warm plate and set aside.

Season the steak cubes: Pat the trimmed sirloin steak cubes thoroughly dry with paper towels (moisture prevents a crusty sear). Season generously on all sides with coarse kosher salt and cracked black pepper right before cooking.

High-heat steak sear: Add 1 tablespoon olive oil to the smoking hot cast iron skillet. Place the steak cubes in a single layer with space between them (cook in two batches if necessary to avoid crowding). Sear undisturbed for 2 minutes to form a deep mahogany crust, then flip and sear for another 1 to 2 minutes for medium-rare to medium tenderness.

Melt garlic herb butter & baste: Reduce the heat to medium-low. Drop the cold cubed European butter, minced garlic, chopped rosemary, and fresh thyme directly into the skillet. As the butter foams and sizzles, use a large spoon to baste the foaming herb butter continuously over the steak bites for 60 seconds.

Combine, glaze & serve: Return the crispy golden potatoes to the skillet, tossing gently with the steak cubes to coat every morsel in the glossy garlic-herb butter pan sauce. Remove immediately from heat, garnish with fresh minced parsley, and serve sizzling hot straight from the skillet!