Preheat the oven to 400°F with a rack in the center position.Slice off the tops of the garlic and drizzle with the olive oil
Wrap the garlic in foil and place, seam side up, on the center rack
Roast until caramelized and tender, about 40 minutes
Fill a large pot with water and add the potatoes, bay leaves and 3 teaspoons of the salt
Bring to a boil over high heat, then reduce the heat to low and simmer until the potatoes are fork tender, about 15 minutes
Drain.Return the potatoes to the pot
Discard the bay leaves
Using a potato ricer or masher, mash the potatoes
Once the garlic has cooled enough to handle, gently squeeze the roasted garlic cloves into the pot with the mashed potatoes and mash to combine.Place the butter, milk and remaining salt in a small saucepan
Cook over medium-low heat until the butter has melted and the mixture is hot, but not boiling
Pour the mixture into the potatoes, stirring quickly with a large spoon until fully absorbed
Season with salt and pepper to taste
