Cut each potato into 6 long wedges. Save 4 wedges. Juice the remaining wedges in an electric vegetable juicer, and pour the juice through a fine mesh strainer. This will yield approximately 4 cups. Allow the juice to stand for 2 hours. A layer of white starch will form at the bottom of the juice. Pour the juice off the starch into a medium saucepot. Place over a medium flame and reduce to one cup or until the sauce naturally thickens. Remove from the fire and stir in the ginger and Thai chili pepper. Stir until the sauce tastes spicy enough and strain immediately. Split each poached parsnip in half lengthwise and rub with a small amount of grapeseed oil. Rub the 4 reserved sweet potato wedges with grapeseed oil. Season the parsnip and potato with salt and pepper. Bake on a cookie sheet in a pre-heated 400 degree oven until browned and cooked through (approximately 15 minutes). Heat a large saute pan over a medium heat. Season each duck breast with salt and pepper. Press one side of the duck breast into the coriander seeds. Wipe the saute pan with a towel that has been dipped into grapeseed oil. Add the duck breasts, seed side down. Saute until the coriander browns. Turn the duck breast over and transfer the pan to a 375 degree oven for 3 to 5 minutes. Remove the breasts and allow them to rest 2 to 4 minutes. Set a piece of parsnip and wedge of sweet potato on each plate. Slice each duck breast into 1/4-inch slices and arrange against the vegetables. Spoon sauce onto each plate and garnish with pea shoots.