Whisk salad dressing ingredients together, including the ¼ cup of the liquid from the canned mandarin oranges, adding the olive oil last. Taste and adjust seasoning as needed. Arrange lettuce on a platter, placing the watercress in the center. Surround the watercress with mandarin orange sections, artichoke hearts and julienned chayote. Drizzle dressing over all and serve with additional dressing on the side.
Note: Chayote is a South American squash from the zucchini family. If chayote is not available at your grocer, zucchini can be substituted in this recipe!