Step 1

Preheat: Preheat oven to 400°F. Line a large baking sheet with parchment paper (see note 3).

Step 2

Prep garlic for Soup: Slice top off the head of garlic. Place garlic on foil and drizzle 2 teaspoons of the olive oil over the cut side. Wrap tightly with foil and place on baking sheet.

Step 3

Roast vegetables: Add potatoes, parsnips, leek, and onion to baking sheet. Drizzle with the remaining 2 tablespoons of olive oil. Toss to coat. Sprinkle with ¼ teaspoon of the salt. Bake until fork tender and golden brown on the edges, about 40 minutes, flipping vegetables halfway through.

Step 4

Make Chive Gremolata: Meanwhile, in a small bowl, stir together chives, parsley, lemon zest, salt, and red pepper flakes (to taste). Cover and refrigerate until needed.

Step 5

Blend soup: Transfer roasted vegetables to a blender. Unwrap and squeeze head of garlic over blender, to release the soft garlic cloves (discard garlic peel). Add vegetable stock, lemon juice, white pepper, and remaining ¼ teaspoon salt. Blend until smooth, thin with more broth if needed. Taste and season with more salt, if needed.

Step 6

Heat soup: If you have a high-speed blender, heat soup directly in blender (see note 4). Otherwise, transfer to a pot over medium heat. Pour hot soup into bowls, garnish with chive gremolata.