Slice the tops off the garlic bulbs to expose the cloves, drizzle with olive oil and a pinch of salt, then wrap tightly in foil and roast at 400°F (205°C) for 40-45 minutes until soft, golden, and caramelized.
Allow roasted garlic to cool slightly, then squeeze the cloves from the skins into a mixing bowl to release the sweet, buttery garlic paste.
Add softened butter, parsley, lemon zest, pepper, and salt to the bowl, then mash and fold the mixture until smooth, creamy, and fully blended.
Taste and adjust seasoning, adding more garlic, salt, herbs, or lemon depending on your desired flavor intensity.
Transfer the garlic butter to a jar or roll it into a log using parchment paper, then chill to firm up or serve immediately for warm dishes and spreads.