Preheat the oven to 425°F (220°C) for the potatoes.
Wash and dice the potatoes into small cubes. Toss them with olive oil, salt, and pepper, then spread them evenly on a baking sheet.
Roast the potatoes in the oven for about 20-25 minutes or until they are crispy on the outside and tender on the inside, stirring halfway through.
While the potatoes are roasting, season the 6 oz sirloin steak generously with salt and pepper.
Heat a skillet over medium-high heat. Add the steak and sear each side for about 3-4 minutes for medium-rare, adjusting time for your preferred doneness.
Once nearly finished with the steak, add the butter and minced garlic to the skillet. Spoon the melted garlic butter over the steak to enhance its flavor.
Meanwhile, blanch the green beans in boiling water for 2-3 minutes until just tender and bright green, then drain.
Plate the steak, roasted potatoes, and green beans together, and drizzle any remaining garlic butter from the pan over the steak.
Serve immediately and enjoy while hot.