If we're going to get historical - watercress was originally introduced to Japan in the 1870s and first called oranda garashi (Dutch mustard). These days it is generally referred to as kureson (from the French cresson). In recent years, this semiaquatic plant has gained popularity, and is now found in as a boiled and seasoned side dish. I once had it as a creamed soup which a Japanese neighbor made for me - I could never recreate that heavenly goodness, no matter how hard I try (I think it's the creamy nature of Japanese milk.)
Children living in the countryside are often surprised to learn that this plant grows wild in many of the nearby mountain streams. Clean and slightly alkaline water is the key. Often during spring field trips, children wade knee-high in icy spring runoff to gather bunches to take home or cook in the classroom. That was how I first stumbled upon kureson - while going on a foraging field trip with my friends one early day in March. The freshly picked greens and my feet freezing from the snow run off was a feeling I will never forget.
If you gather the kureson wild, it is best when eaten in the late spring before it flowers and becomes bitter. (Serves 3-4)
¼ cup rice vinegar
2 tablespoons light soy sauce
¼ cup mirin
2 teaspoons sugar
3 bunches watercress
Bonito flakes or sesame seeds for garnish
1. Make the dressing: Combine the vinegar, soy sauce, mirin, and sugar in a bowl. Cool in refrigerator for later.
2. Cut the watercress into 3- to 4-cm-long pieces. Separate the stem and leaf sections.
3. Blanche the stems in a pot of boiling water, adding the leaves after 30 seconds. (Be careful not to overcook.) Drain and chill the greens in cold water. Drain again, and squeeze out excess water.
4. Add the watercress to the dressing, and mix. Cool in refrigerator for about 10 minutes.
5. Serve the greens, and pour the remaining dressing over the top. Garnish with bonito flakes or sesame seeds.