Preheat oven to 375 F. Slice the tops of the garlic heads off. Drizzle with olive oil and season with salt and pepper to taste. Envelop them with aluminum foil and roast them for 1 hour. Remove the garlic by pushing upward from the bottom of the heads. Mash them with a fork.
Peel and slice your potatoes into chunks. Fill a medium pot with half way of water. Bring to a boil, add 2 tsp salt and the potatoes. Bring back to a boil and cook for 10 minutes or until you can easily fork the pieces. Drain the water from the pot and let them sit in the pot for 1 minute for all liquid to evaporate.
In a small pan, melt your butter on medium heat. Add in the milk and mashed garlic and bring to a simmer. Cook until mostly combined - about a minute or two. Add this mixture to your potatoes and season with salt and pepper to taste. Mash them to your desired texture and consistency. If they are too thick you can add a little bit at a time of milk to make them more mushy. Top with chives.