Preheat the oven to 350°F. Place the garlic cloves in an ovenproof dish and drizzle with olive oil. Place the dish, uncovered, in the oven for 15-20 minutes until the garlic is golden brown and soft. Remove from the oven and let cool. Peel the potatoes and cut them in half. Place them in a pot and cover with cold water. Bring to a boil over high heat and simmer until the potatoes are tender when pricked with a fork, about 30 minutes depending on the size of the potatoes. Drain. Bring the stock to a boil, and turn down to a simmer. Squeeze the roasted garlic clove to release each clove of garlic. Mash the garlic with a fork and throw the skins away. Mash the potatoes with a potato masher or fork, or use a food mill. Add the roasted garlic. Slowly add the stock until the desired consistency is reached.