Cut the top ¼” to ½” off of a whole head of garlic, so that each individual clove should be visible. Make sure every garlic clove is exposed.
Place the head of garlic on foil paper together with the thyme. Drizzle the top of the garlic with a bit of oil, about 1 teaspoon. Wrap it up and place it in the oven to roast for about 30 minutes or more. It should be soft, fragrant, and golden. Let the garlic cool, then squeeze individual cloves out of the skin.
Peel the potatoes, removing any spoiled spots, such as bruising and discoloration.
Cut into big even sized chunks. Place potatoes in water as you peel to prevent discoloration.
Wash the potatoes and rinse until water runs clear. Place the potatoes in a large pot with about 1 -2 teaspoons of salt and enough water to cover the potatoes.
Bring to a boil. Cook until potatoes are fork tender. Be sure to drain the potatoes after cooking . Then gently reheat the drained potatoes on the stovetop to remove moisture from the potatoes .
Transfer potatoes to a stand mixer attached with a whip paddle. Then, add butter, sour cream, garlic, and black pepper. Start mixing while adding warm milk as you go until the mashed potatoes are whipped and fluffy. You may add more milk if desired .
If using a potato ricer, press potatoes and garlic into large bowl. Add, butter, sour cream , milk ; stir to blend. Season to taste with salt and pepper
Adjust salt and pepper. Garnish with parsley. Serve warm.