Preheat oven to 375°F.
Slice ¼ inch off the top of the garlic bulb. Place the bulb, cut side up, on a 12x12 inch piece of aluminum foil, folded in half. Pour the olive oil over the top of the cut garlic bulb. Pull the edges of the foil around the garlic bulb to enclose the garlic in foil.
Place in the oven and roast for 45–60 minutes, or until the garlic cloves are deep brown. Squeeze the roasted garlic out of the skin.
Meanwhile, cut the cauliflower into large florets. Place the florets and ¾ cup of chicken stock in a saucepan over medium heat. Bring the stock to a boil, cover, and cook for 10–12 minutes, or until the cauliflower is tender.
Use a slotted spoon to place the steamed cauliflower into the bowl of a food processor, along with ¼ cup of the remaining chicken stock. Add the roasted garlic, butter, and kosher salt.
Cover the food processor, leaving a vent for steam, and process until smooth. If necessary, add more of the chicken stock to create a smooth texture.
Place in a serving dish, garnish with parsley, and serve.