60 mL (4 Tbsp) unsalted butter
2 large yellow onions, chopped
12 large carrots, peeled and chopped
2 L (4 cups) chicken stock
250 mL (1 cup) orange juice, freshly squeezed
Salt and freshly ground black pepper, to taste
Grated fresh orange zest, to taste
Melt butter in a pot. Add the onions, cover and cook over low heat until tender and lightly coloured, about 25 minutes. Add carrots and stock and bring to a boil. Reduce heat, cover, and simmer until carrots are very tender, about 30 minutes.
Pour the soup through a strainer and transfer the solids to the bowl of a food processor fitted with a steel blade (alternatively a blender or a food mill fitted with a medium disk). Add 1 cup of cooking stock and process until smooth. Return purée to pot and add the orange juice and 2-3 cups of the remaining stock, until the soup is the desired consistency.
Season to taste with salt and pepper; add orange zest. Simmer until heated through. Serve immediately.