Place the diced Yukon gold potatoes in a microwave-safe bowl with 1 tablespoon of water, cover with a damp paper towel, and par-cook for 3 minutes (this creates ultra-crispy edges without raw centers). Pat completely dry.

Heat 2 tablespoons of olive oil and 1 tablespoon of butter in a large 12-inch heavy cast-iron skillet over medium-high heat. Add the potatoes in a single layer. Season with kosher salt, black pepper, and smoked paprika. Cook undisturbed for 4 minutes until deeply golden on the bottom, then flip and sauté for another 3 to 4 minutes until fork-tender and blistered on all sides. Transfer to a warm plate.

Pat the cubed sirloin steak dry with paper towels. Season generously on all sides with kosher salt, coarse black pepper, and garlic powder.

Increase the skillet heat to high. Add 1 tablespoon of olive oil. Once shimmering and smoking hot, add the steak bites in a single layer with space between cubes (cook in two quick batches if needed to avoid steaming). Sear undisturbed for 2 minutes until a deep, dark caramelized crust forms, then flip and sear for 1 to 2 minutes more for medium-rare to medium tenderness. Remove and rest with the potatoes.

Lower heat to medium. Melt the remaining 3 tablespoons of butter in the skillet drippings. Add the minced garlic, fresh rosemary, and fresh thyme. Sauté for 45 to 60 seconds until fragrant and foaming, basting the aromatic butter continuously.

Toss the seared steak bites and crispy potatoes back into the bubbling skillet. Spoon the rich foaming garlic herb butter generously over everything for 1 minute until glistening and heated through.

Remove from heat immediately to prevent overcooking the steak. Garnish with chopped fresh flat-leaf parsley and flaky sea salt. Serve hot straight from the skillet!