Pat potato cubes completely dry with paper towels. Heat 1 tbsp olive oil in a large skillet over medium-high heat. Add potatoes in a single layer and cook undisturbed for 5 minutes until golden on one side.
Stir potatoes, season with 1/2 tsp salt and 1/4 tsp pepper. Reduce heat to medium, cover, and cook 10–12 minutes, stirring occasionally, until tender and golden brown. Transfer to a plate.
Increase heat to high. Add remaining 1 tbsp olive oil to skillet. Season steak cubes with remaining salt, pepper, and paprika. Add steak in a single layer (work in batches if needed) and sear 2–3 minutes per side until browned. Remove steak.
Reduce heat to medium-low. Add 4 tbsp butter and minced garlic to skillet. Cook 1 minute until fragrant but not browned. Stir in herbs.
Return steak and potatoes to skillet. Add remaining 2 tbsp butter. Toss everything together for 1–2 minutes until coated and heated through. Taste and adjust seasoning.
Spoon steak bites and potatoes onto a white plate side by side. Drizzle with any remaining garlic butter from the pan. Garnish with extra parsley if desired.