Preheat your oven to 425°F.
Toss the baby potatoes with olive oil, a pinch of salt, and black pepper, then spread them out on a baking sheet.
Roast the potatoes in the oven for 20-25 minutes until crispy and golden, turning once halfway through.
Meanwhile, trim the green beans and toss them with a little olive oil, salt, and pepper. Spread them on another baking sheet and roast for about 15 minutes until tender and slightly crisp.
Season the sirloin steak generously with salt and pepper on both sides.
Heat a skillet over medium-high heat. Sear the steak for about 3-4 minutes on each side for medium-rare (adjust timing for your preferred doneness).
In the final minute of cooking, add butter and minced garlic (smashed or finely chopped) to the skillet, spooning the melted garlic butter over the steak.
Remove the steak from the skillet and let it rest for a few minutes.
Plate the steak with a side of the crispy roasted potatoes and green beans, drizzling any remaining garlic butter from the skillet over the top.