"One of our favorite salads. When I serve it at parties I always get requests for the recipe. I usually make the dressing and chop the vegetables ahead of time and assemble right before dinner. Serve with French bread croutons."
Place 2 ring molds, 3 to 4 inches each, in the center of 2 salad plates. Arrange watercress around the molds.
Whisk Dijon mustard, white wine vinegar, and salt in a small bowl. Pour in olive oil slowly, whisking constantly, until dressing is thick and smooth. Stir in shallots, parsley, and thyme.
Toss tomato with 1 tablespoon of the dressing and 1 teaspoon of the chives. Spoon tomato into the ring molds. Repeat with avocado, cucumber, hearts of palm, artichoke hearts, and crabmeat, pressing each layer down with the back of a spoon.
Remove ring molds carefully; drizzle remaining dressing over watercress.