Preheat the oven to 425°F for the roasted baby potatoes.
Toss the baby potatoes with a drizzle of olive oil (optional, if within calorie limits), salt, pepper, and half of the fresh herbs.
Spread the potatoes on a baking sheet and roast in the oven for 20-25 minutes until golden and tender.
While the potatoes are roasting, season the sirloin steak generously with salt and pepper.
Heat a heavy skillet or cast-iron pan over medium-high heat.
Sear the steak for about 3-4 minutes on each side for medium-rare, adjusting time as needed for desired doneness.
In the last minute of cooking, add the butter, garlic, and remaining herbs to the pan. Spoon the melted herb-garlic butter over the steak to infuse flavor.
Remove the steak from the pan and let it rest for a few minutes before slicing.
Plate the sliced steak alongside the roasted baby potatoes and drizzle any remaining butter from the pan over the top.