9 ounces carrots, peeled and chopped
9 ounces sweet potatoes, peeled and chopped
9 ounces parsnips, peeled and chopped
9 ounces celery root, peeled and chopped
1 teaspoon cumin seeds, toasted in a dry pan until darkened and aromatic
1/2 to 1 teaspoon crushed dried chili
3 tablespoons olive oil
1 ounce butter
5 ounces red onions, peeled and chopped
1 large leek, cleaned, trimmed, and chopped
Salt and freshly ground pepper
Balsamic reduction:
1/2 cup balsamic vinegar
1 tablespoon dark molasses
Heat the oven to 375°F. Set half the carrots aside and put the rest of the carrots, the sweet potatoes, parsnips, and celery root in a baking pan. Add the spices, salt and pepper, and 2 tablespoons of the oil and shake the pan until the vegetables are coated with oil. Place in the middle of the oven for up to 45 minutes, checking and turning from time to time until the vegetables are soft and browned.
Meanwhile, heat the remaining tablespoon of oil and the butter in a large pan with a lid. Add the onions and cook on a gentle heat until translucent, about 5 minutes.
Add the remaining carrots and the leek to the onions. Cover the pan and cook for 20 minutes, stirring occasionally to make sure the vegetables do not burn or stick to the pan. If the mixture becomes too watery, uncover the pan until all the liquid has evaporated.
Add 6 or 7 cups of water, the roast vegetables, and plenty of salt to the pan. Simmer for a further 10 minutes. Remove from the heat and leave to cool a little, then whiz in a blender until smooth.
While soup is cooking, make the balsamic reduction:
Combine the vinegar and molasses in a small saucepan. Bring to a simmer over medium heat; cook, stirring occasionally, until the amount is reduced by about half and the mixture is maple-syrup consistency, about 8 minutes. Transfer to a bowl. Cover and refrigerate; the mixture will continue to thicken as it cools. Drizzle each serving of soup with a swirl of the balsamic reduction.
Serves 4.
From Sophie Conran's Soups and Stews, with minor changes