Preheat oven to 400F.
Slice top ½ inch of garlic head so all cloves are showing. Add garlic to large piece of foil and drizzle with olive oil, then wrap completely. Place garlic on baking sheet and bake for about 50 minutes, or until garlic is fragrant, tender, and lightly browned.
To a large stockpot, add water, potatoes, and 1 tablespoon salt and bring to a boil. Cook for about 8-10 minutes, or until tender when pierced with a fork. Drain and rinse potatoes.
Mash potatoes with potato masher or sturdy whisk.
Add in roasted garlic, butter, cream cheese, onion powder, remaining salt, and pepper and stir while slowly adding in half and half. Do not add all the liquid at once.
Taste for additional seasoning, stir in chives, and serve immediately.