- Preheat oven to 300 degrees.
- Light grill or preheat grill to medium.
- Peel parsnips, and then quarter lengthwise. Drizzle with grapeseed oil, salt, and pepper.
- Place parsnips on grill over medium heat and cook until almost tender.
- Transfer to an 8 x 8-inch baking pan. Add vegetable stock and head of garlic, and cover. Place in oven, and bake 30 minutes or until very tender.
- Remove parsnips from pan and place in blender. Purée until smooth, using remaining cooking liquid as needed to achieve smooth consistency. Season to taste.
- Season shrimp with salt and pepper and lightly toss with grapeseed oil. Grill over medium heat until cooked through.
- Sauté black trumpet mushrooms over medium- high heat. Season with salt and pepper.
- To serve, top purée with shrimp, mushrooms, and clementine segments.