Preheat oven to 220° C. Place the parsnips into a mixing bowl, and sprinkle with 1 olive oil. Toss to coat, then season with salt and pepper and spread evenly over a baking sheet. Roast in preheated oven until tender and golden brown, about 30 minutes. Heat 1 tablespoon of olive oil in a large saucepan over medium heat. Stir in the onion and celery. Cook and stir until the vegetables have softened. Reduce the heat to low, and stir in the butter, garlic, brown sugar, and the roasted parsnips and carrots. Continue to cook and stir until all of the vegetables are tender, about 10 minutes. Season with the spices and stir for 1 minute. Pour in the chicken stock, and bring to a boil. Reduce heat and simmer gently for 15 minutes. Puree in a blender or using a stick blender until smooth in texture. Pour into a clean pot and stir in the milk and cream. Return to a simmer over medium-low heat. Season to taste with salt and pepper.