Preheat oven to 400°F. Cut the top off the garlic bulb, drizzle with olive oil, wrap in foil, and roast 30–35 minutes until soft and golden.
Boil potatoes in salted water until fork-tender, 15–20 minutes. Drain and let excess moisture evaporate.
Squeeze roasted garlic into the potatoes. Mash with butter and heavy cream until smooth.
Season with basil, thyme, salt, and pepper. Mix well and serve hot with optional garnish.