Preheat oven to 350º F.
Remove outer layers of garlic head and bake on a baking sheet for 40 to 45 minutes or until soft.
Let cool, then separate cloves from the head and squeeze the soft pulp out of each clove into a small bowl.
Discard the skins.
Cover diced potatoes with water in large saucepan and bring to boil.
Simmer, covered until potatoes are tender, about 20 to 25 minutes, drain.
In a large bow, combine potatoes with butter and stir.
Add milk and garlic pulp, mash until potatoes are smooth and fluffy. Add more milk if needed.
Season with salt and pepper. Sprinkle with scallions or chives on top and serve.