Preheat the oven to 400°F (200°C). Rub the rack of lamb with olive oil, salt, pepper, rosemary, and thyme. Let it sit at room temperature for 20 minutes.

Cook the Potatoes

In a large pot, boil the diced gold potatoes in salted water until tender, about 15-20 minutes. Drain and return to the pot.

Mash the Potatoes

Add heavy cream, butter, chives, salt, and pepper to the drained potatoes. Mash until creamy and set aside.

Prepare the Vegetables

Toss the parsnips and carrots with olive oil, salt, pepper, and thyme sprigs on a baking sheet.

Cooking

Roast the Vegetables

Place the baking sheet with parsnips and carrots in the preheated oven and roast for 25-30 minutes, or until caramelized and tender.

Sear the Lamb

In a hot skillet, sear the rack of lamb on all sides until browned, about 3-4 minutes per side.

Finish in the Oven

Transfer the seared rack of lamb to the oven and roast for about 15-18 minutes for medium-rare. Use a meat thermometer to check for an internal temperature of 135°F (57°C).

Rest the Lamb

Remove the lamb from the oven and let it rest for 10 minutes before slicing.