Begin by placing the halved or quartered baby potatoes in a large pot filled with salted water. Bring the water to a rolling boil over high heat and cook the potatoes for about 12-15 minutes, or until they are fork-tender yet still hold their shape. Once done, drain the potatoes thoroughly and let them sit for about 5 minutes to cool slightly.

Using a fork, gently smash each potato piece to create rough, craggy surfaces. Set the smashed potatoes aside.

Pat the bite-sized pieces of sirloin steak completely dry with paper towels. Generously season the steak with salt and pepper.

In a large cast-iron skillet, heat 2 tablespoons of olive oil over high heat until shimmering. Carefully add the seasoned steak bites in a single layer, and cook undisturbed for 2-3 minutes before flipping and cooking for another 1-2 minutes.

In the same skillet, add the remaining olive oil and arrange the smashed potatoes cut-side down. Cook for about 4-5 minutes until golden and crisp, then carefully flip the potatoes and crisp the other side for an additional 3-4 minutes.

Reduce the skillet's heat to medium-low and add 3 tablespoons of butter along with the minced garlic. Sauté for about 1 minute until fragrant, then add the dried thyme and rosemary, mixing to infuse flavors.

Return the steak bites to the skillet with the potatoes and gently toss for 1-2 minutes until heated through. Adjust seasoning with salt and pepper.

Transfer the garlic butter steak bites and potatoes to a serving platter and sprinkle with freshly chopped parsley before serving.