Preheat oven to 400°F and line a large baking sheet with parchment paper.

Chop potatoes and parsnips into similarly sized cubes. Roughly chop onion. Add potatoes, parsnips and onion to baking sheet. Drizzle with 2 tablespoons olive oil and toss to coat.

Slice the top end off the head of garlic. Place garlic on a piece of tinfoil. Drizzle with remaining 2 teaspoons of olive oil, and then wrap garlic in tinfoil. Place garlic on baking sheet with remainder of the veggies. Roast veggies for 40 minutes, or until the potatoes and parsnips are fork-tender. Flip vegetables half way through for even cooking.

Once veggies are roasted, add them to a blender. Squeeze the garlic bulb to release the roasted garlic into the blender. Add hot vegetable stock, and then blend until smooth. Be careful when blending, mixture will be hot! Add lemon juice, salt and white pepper. Blend to mix. Serve immediately and top generously with Chive Gremolata.