(THE WASHINGTON POST) - For decades, vegetarians have looked to global cuisines for inspiration.

The pioneer was Anna Thomas, author of The Vegetarian Epicure, a 1972 bestseller. As Jonathan Kauffman writes in his captivating new book, Hippie Food, at a time when much vegetarian food was brown-on-brown, Thomas "pored over Italian and Middle Eastern cookbooks, in which vegetables were integrated in ways meat-and-potato Americans never imagined". For the book's sequel, she traveled widely and wrote firsthand about dishes from throughout Europe, the Middle East, Mexico and more.

Thomas's influence extended not just to virtually every vegetarian restaurant of the time, but to the spate of vegetarian cookbooks that followed.

"For a short period, vegetarians were the culinary avant-garde, evidence that Americans - particularly white Americans - were emerging from an era of dominant-culture assimilation into a multicultural one," Kauffman writes.

I thought about Kauffman's take, and Thomas's influence, when I paged through yet another book, Rebecca Seal's Lisbon: Recipes From The Heart Of Portugal, looking for ideas for something different to satisfy me this cold winter. I hit on a recipe for Watercress Soup, a Portuguese staple that adds the green to a simple base of pureed potato, carrot and sometimes turnip.

I've never been to Portugal, but Seal's prose and recipes took me there, and I was thrilled to read that in addition to the chorizo pâté and the salt cod croquettes, the pork with clams and the chicken pies, she found a Portuguese love for broad beans, pumpkin, chickpeas - and this traditional soup.

She writes that some families add small pasta or barley to make it even heartier, but I wanted to keep it as simple as possible. Simple it is: You cook the aromatics and roots in broth, puree, add a little butter for richness, and fold in the chopped watercress. The result is silky and mild, with little bursts of peppery flavour from the greens.

This simple but lively soup can get enriched with a little butter, but to make it vegan you can omit it, or use olive oil instead.

It's satisfying, and it's different, just like I wanted.

Watercress Soup

4 to 6 servings (makes about 8 cups)

Serve with crusty bread.

Adapted from Lisbon: Recipes From The Heart Of Portugal, by Rebecca Seal (Hardie Grant Books, 2017, $52.99 from www.kinokuniya.com.sg).

INGREDIENTS

2 Tbs extra-virgin olive oil

1 yellow or white onion, chopped

396g potato, peeled and cut into 1cm dice

2 medium carrots, scrubbed well and cut into 1cm dice

4 cloves garlic, crushed

5 1/2 cups no-salt-added vegetable broth, heated

1 tsp sea salt, or more as needed

1/4 tsp freshly ground black pepper, or more as needed

140g fresh watercress

2 Tbs unsalted butter (optional; may substitute extra-virgin olive oil)

METHOD

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

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