1. Boil a large pot of water. Preheat oven to 400 degrees F. Cut very tip off garlic head, and place garlic on top of a cookie sheet; drizzle olive oil and salt, and place in oven.
2. Place potatoes in boiling water. Cooking time for both potatoes and garlic is 30-40 minutes. When a small knife is poked into potato and it slides off without any force or shake, the potatoes are ready.
3. Take the garlic out of the oven, and set it aside to rest. Pour the potatoes out onto a colander to fully drain out all the water. Place the potatoes back into the pot and turn the heat back up to medium-high until you no longer hear any sounds, about 3-5 minutes.
4. Squeeze the garlic out of its skin, and place the garlics into the pot with the potatoes; start mashing. Mash to your liking (silky smooth, with little lumps, or with bite size chunks).
5. Add salt, black pepper, margarine, and milk. Fold into potatoes until equally incorporated. Scoop out onto a serving dish. Serve and enjoy!