Look for watercress at Asian groceries; I find that it is invariably fresher and more plentiful there than in the regular grocery stores.
Watercress and Cabbage Stir-Fry
1 tablespoon vegetable oil
2 cloves garlic, minced
1/2 medium green cabbage, sliced and diced
1 large bunch watercress
2 tablespoons soy sauce
1 tablespoon toasted sesame oil
In a large skillet heat the oil over medium-high heat. When the oil is hot, add the garlic and diced cabbage and cook, stirring frequently, for about 2 minutes. Chop off the bottom halves of the watercress stalks and set aside for another purpose. Chop the leaves and tender upper stalks. Add the chopped watercress, soy sauce, and sesame oil and cook for another few minutes, or until the watercress is wilted and the cabbage is of the consistency you prefer.
(Image: Faith Durand)