Preheat the oven to 425°F for the baby potatoes.
Wash the baby potatoes and cut them in halves if they are larger. Toss them with olive oil, salt, pepper, and finely chopped rosemary and thyme.
Spread the potatoes on a baking sheet and roast for about 20-25 minutes until golden and tender, stirring halfway through.
While the potatoes roast, season both sides of the sirloin steak generously with salt and pepper.
Heat a skillet over medium-high heat. Add a small amount of olive oil along with the garlic clove (slightly crushed) and allow the flavors to infuse.
Sear the steak for about 3-4 minutes on each side to achieve a nice crust, adjusting the cooking time as needed depending on thickness and desired doneness.
In the last minute of cooking, add the unsalted butter to the pan and baste the steak with the melted herb-garlic butter.
Remove the steak from the skillet and let it rest for a few minutes before slicing.
Plate the sliced steak along with the roasted baby potatoes and drizzle any remaining herb-garlic butter over the top for extra flavor.