Split each poached parsnip in 1/2 lengthwise and rub with a small amount of grapeseed oil. Rub the 8 sweet potatoes wedges with grapeseed oil. Season the parsnip and potato with salt and pepper. Bake on a sheet tray in a pre-heated 400 degree oven until browned and cooked through (approximately 15 minutes). Heat a large, nonstick saute pan over medium heat. Season each duck breast with salt and pepper. Press one side of the duck breast into the coriander seeds. Use a squeeze bottle to drizzle a thin line of grapeseed oil over the coriander on each duck breast. Add the duck breasts, seed side down to the hot saute pan. Saute until the coriander browns. Turn the duck breasts over and set the pan off the flame for 3 to 5 minutes. Remove the breasts and allow them to rest 2 to 4 minutes. To plate, 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.
Juice sweet potatoes and allow the juice to stand for 4 hours. This will allow much of the potato starch in the juice to settle. Pour the juice through a fine mesh strainer being careful to leave the settled starch behind. Place over a medium flame and reduce to approximately 1 1/2 to 2 cups, or until the sauce naturally thickens. Remove from the fire and stir in the ginger and Thai chile pepper. Stir until the sauce tastes spicy enough and strain immediately. Season to taste with salt, pepper, and lemon juice.