Preheat oven to 375 degrees F.
In a large roasting pan toss potatoes and parsnips with garlic cloves in olive oil. Season with salt and plenty of cracked black pepper. Roast for 40 to 45 minutes or until potatoes and parsnips are golden and tender. Toss occasionally to prevent garlic from burning. Remove from the oven and. mash directly in the pan with a hand masher. Add cream, butter, sour cream and fresh chives and stir just to blend and season again to taste.