At the Yi Xin vegetarian restaurant in Guangzhou, my favorite dish is a soup featuring pea shoots, the tender, delicate leaves and tendrils of green peas. The first time I had that soup, it was so fragrant with a silky richness that I could’ve sworn it was a meat-based broth. Later I learned that the vegetarian chefs add flavor and body to the soup by simply toasting flour and stirring it with sesame oil to form a base similar to a roux. To enjoy, eat the tender cooked greens with chop-sticks and then sip the velvety, quietly sustaining broth. Feel free to use spinach or tender napa cabbage hearts instead of pea shoots for a different but equally delicious result.
- Keep the leaves and crisp stems of the pea shoots and pluck off any hard tendrils and stems tough enough to bend without breaking. Wash well and drain. In a small bowl, soak the goji berries (if using) in cool water to plump.
- Bring a pot of water to a boil and blanch the pea shoots until just wilted, about 20 seconds. Drain in a colander and shake dry. This step will prevent them from later turning the soup an unpleasant brownish color.
- Heat a dry wok over low heat. Add the flour and toast, stirring continuously, until pale yellow and faintly fragrant, about 1 minute. Stir in the sesame oil to form a smooth paste and cook, stirring continuously, for 2 to 3 minutes, until the mixture is golden in color.
- Add the stock and raise the heat to medium. The soup will look curdled and separate at first, but continue stirring from the bottom and it will come together. Bring the mixture to a gentle boil and, using a ladle, skim off any foam that rises to the top. The soup should look creamy in color and very smooth in consistency. Season with the salt.
- Add the mushrooms, reduce the heat to low, and simmer for 3 minutes to cook through. Add the blanched pea shoots and cook for about 2 minutes to heat them up. Taste and add more salt if necessary. Transfer to a large soup tureen or ladle into bowls. Garnish with a few goji berries, if desired, and serve immediately.