2 tablespoons extra-virgin olive oil
1 yellow or white onion, chopped
One 14-ounce potato, peeled and cut into ½-inch dice
2 medium carrots, scrubbed well and cut into ½-inch dice
4 cloves garlic, crushed
5½ cups no-salt-added vegetable broth, heated
1 teaspoon sea salt, or more as needed
¼ teaspoon freshly ground black pepper, or more as needed
5 ounces fresh watercress
2 tablespoons unsalted butter (optional; may substitute extra-virgin olive oil)
Pour the oil into a large saucepan over medium heat. Once the oil shimmers, add the onion, potato and carrots. Cook, stirring often, until the onion starts to soften, 5 minutes. Add the crushed garlic and cook, stirring, for 1 minute.
Add the hot broth, salt and pepper. Once the liquid starts to bubble, reduce the heat to medium-low, cover and cook until the vegetables are tender, 30 minutes.
While the soup is cooking, rinse the watercress and remove any large or tough stems. Reserve 4 to 6 whole sprigs to garnish the soup, then coarsely chop the rest of the watercress.
Once the soup vegetables are tender, remove the saucepan from the heat. Use an immersion (hand-held/stick) blender to puree the soup until smooth. (Alternatively, you can use a jug blender, working in batches if necessary to avoid filling more than halfway, to prevent splatters.) Add the butter, if using, stirring until it has melted. Taste, and add more salt and/or pepper, as needed.
Return the soup to medium heat and bring to a very gentle bubble, then add the chopped watercress. Cook just until the watercress wilts, a minute or two, then divide among serving bowls, garnishing each with a reserved sprig of watercress. Serve hot with crusty bread.
Serves 4 to 6 (makes about 8 cups)
Nutrition | Per serving (based on 6, using butter): 160 calories, 2 g protein, 21 g carbohydrates, 9 g fat, 3 g saturated fat, 10 mg cholesterol, 410 mg sodium, 1 g dietary fiber, 6 g sugar
Nutrition | Per serving (based on 6, without butter): 130 calories, 2 g protein, 21 g carbohydrates, 5 g fat, 1 g saturated fat, 0 mg cholesterol, 410 mg sodium, 1 g dietary fiber, 6 g sugar
Adapted from "Lisbon: Recipes From the Heart of Portugal," by Rebecca Seal (Hardie Grant Books, 2017).