Preheat your oven to 400°F (200°C). Peel away the outer layers of the garlic head, leaving the cloves intact. Cut about 1/4 inch off the top to expose the cloves.
Drizzle the exposed garlic with olive oil and wrap it tightly in aluminum foil. Place on a baking sheet and roast for 30-35 minutes, or until soft and caramelized. Allow to cool slightly.
Squeeze the roasted cloves out of their skins into a mixing bowl. Mash the garlic until smooth using a fork or potato masher.
Add the softened butter, chopped parsley, and kosher salt to the bowl. Mix until well combined and creamy.
Transfer the butter to parchment paper or plastic wrap, shape into a log, twist the ends to seal, and refrigerate until firm.
