Roast the Garlic: Preheat your oven to 350°F (175°C). Drizzle olive oil over the top of the garlic head, wrap it in aluminum foil, and roast it in the oven for 1 hour until soft and fragrant.

Prepare the Potatoes: While the garlic is roasting, bring a large pot of salted water to a boil. Add the peeled and quartered russet potatoes and cook until tender, about 15 minutes. Drain and allow the potatoes to cool for a few minutes.

Mash the Potatoes: Transfer the potatoes to a mixing bowl. Add milk, butter, salt, and pepper. Use an electric mixer to mash the potatoes until smooth and creamy. Adjust the consistency with more milk if needed.

Add the Roasted Garlic: Once the garlic is done roasting, cut the head in half and squeeze the softened cloves into the mashed potatoes. Mix everything together until the garlic is evenly distributed.