Pat potato cubes dry with paper towels. Heat 1 tbsp olive oil in a large skillet over medium-high heat. Add potatoes in a single layer, season with 1/2 tsp salt and 1/2 tsp pepper. Cook undisturbed for 5-7 minutes until golden brown on one side, then toss and cook another 5-7 minutes until crispy and tender. Transfer to a plate.

Pat steak cubes dry and season with remaining salt, pepper, and paprika if using. In the same skillet, heat remaining 1 tbsp olive oil over high heat. Add steak in a single layer, searing for 2-3 minutes per side until browned and medium-rare. Remove steak and set aside with potatoes.

Reduce heat to medium-low. Add 4 tbsp butter to the skillet. Once melted, add minced garlic and cook for 1 minute until fragrant but not browned. Stir in remaining 2 tbsp butter until melted and saucy.

Return potatoes and steak bites to the skillet. Toss gently to coat everything in the garlic butter sauce. Cook for 1-2 minutes to reheat. Remove from heat, stir in chopped parsley, and adjust seasoning if needed.