Combine olive oil, garlic, rosemary, thyme, salt, and pepper.
Rub the mixture over the lamb chops and marinate for 30 minutes.
Boil potatoes until tender, about 15 minutes.
Drain and mash with butter, cream, roasted garlic, salt, and pepper.
Heat a grill pan over medium-high heat.
Grill lamb chops for 3–4 minutes per side for medium-rare.
Melt butter in a small saucepan.
Add garlic, thyme, rosemary, and lemon juice.
Simmer for 1 minute.
Arrange mashed potatoes on a serving plate.
Place lamb chops on top and drizzle with herb butter sauce.
Garnish with rosemary sprigs and roasted garlic cloves.