1. In a bowl, mix vinegar, shallot, and honey. Whisking constantly, slowly drizzle in 1/3 cup olive oil and whisk until mixture is thick and emulsified. Season to taste with salt and pepper. Add watercress and mix to coat with dressing.
2. Lift watercress from dressing and spread equally on six salad plates. Arrange tomatoes around watercress and set a chunk of cheese alongside. Sprinkle salads lightly with more salt and pepper, and drizzle tomatoes and cheese with a little more olive oil.