Place halved baby potatoes in a microwave-safe bowl with 1 tbsp water. Cover and microwave on high for 3 minutes to par-cook; drain well.
Heat 1 tbsp olive oil and 1 tbsp butter in a 12-inch cast iron skillet over medium-high heat. Add potatoes cut-side down, season with 1/2 tsp salt, 1/4 tsp pepper, and smoked paprika. Sear undisturbed for 5-6 minutes until crispy and golden. Transfer to a plate.
Pat steak cubes completely dry with paper towels. Season with remaining salt, pepper, and garlic powder.
Add remaining 1 tbsp olive oil to smoking hot skillet. Add steak bites in a single uncrowded layer. Sear undisturbed for 2 minutes to form a dark crust, then flip with tongs and cook for 1-2 minutes more.
Reduce heat to medium-low. Add remaining 3 tbsp butter, minced garlic, rosemary, and thyme to the skillet. Baste steak bites continuously with foaming garlic butter for 30-45 seconds.
Return golden potatoes to skillet and toss everything together to coat in savory garlic herb pan juices.
Remove from heat, garnish with fresh parsley and flaky black pepper, and serve immediately straight from the skillet!