Make the vinaigrette: In a small non-reactive bowl or food processor, place the shallots, mustard, honey, vinegars, and fruit juices and whisk or process. Slowly incorporate the oils, teaspoon by teaspoon until emulsified. Add salt and pepper to taste.
In a small saute pan heat the sesame oil until just below the smoking point. Add the sesame seeds and cook until the oil colors slightly. Drain the oil and reserve the seeds.
In a large bowl combine 1/2 of the sesame seeds, the watermelon, watercress, parsley, scallions, and chervil and toss with the vinaigrette to taste. Divide the greens between 6 or 8 individual salad plates and place the watermelon pieces on top. Sprinkle with the reserved sesame seeds and serve immediately.