Preheat the oven to 375 degrees F. Chop the top off of the bulb of garlic, drizzle with olive oil, and wrap in foil. Place in the preheated oven and roast 35 to 45 minutes, until garlic cloves are soft and golden brown. Allow garlic to cool enough to handle, then peel the cloves.

Heat a full pot of water to boiling and peel potatoes. Chop potatoes into quarters and carefully drop them into the water. Return water to a controlled boil and cook for 15 to 20 minutes, or until potatoes are very soft when poked with a fork. Strain potatoes into a colander and set aside.

Heat butter over medium heat in the same pot you used to boil the potatoes. Add the kale, and chopped green onions. Sauté, stirring frequently, until kale has softened, about 3 minutes.

Remove pot from heat. Add the cooked potatoes, roasted garlic, buttermilk, and sea salt. Mash potatoes using a potato masher or fork until potatoes reach the desired texture.

Taste the mashed potatoes and add sea salt to taste. Serve colcannon with butter and enjoy!