Preheat your oven to 400°F and line a baking sheet with parchment paper.
Dice the Yukon Gold potatoes into small 1/2-inch cubes to ensure they get maximum crispiness.
Toss the potatoes on the baking sheet with 0.5 tbsp of avocado oil and half of the salt and pepper.
Roast the potatoes for 20-25 minutes, flipping halfway through, until they are golden brown and tender.
While potatoes roast, season the steak on both sides with the remaining salt, pepper, and finely chopped fresh rosemary.
Heat the remaining 0.5 tbsp of avocado oil in a heavy cast-iron skillet over medium-high heat until shimmering.
Place the steak in the hot skillet and sear for 3-4 minutes per side for medium-rare, adding the smashed garlic cloves to the pan during the last 2 minutes to infuse the oil.
Remove the steak from the pan and let it rest on a cutting board for at least 5 minutes to lock in the juices.
While the steak rests, steam the green beans in a small amount of water for 3-4 minutes until they are bright green and crisp-tender.
Slice the steak against the grain and serve immediately with the crispy potatoes and steamed green beans.