1Toast walnuts in a small skillet over medium heat, stirring constantly, until walnuts are fragrant and begin to release oil, 7 to 10 minutes. Set aside to cool thoroughly.
2Dissolve 1/2 teaspoon salt in a bowl of cold water; place pear slices, apple slices, and Asian pear in the water, about 5 minutes; drain.
3Arrange 1 lettuce leaf, 1 watercress leaf, and 1 sliced strawberry decoratively on top of each other on 4 salad plates.
4Whisk yogurt, mayonnaise, and vinegar together in a small bowl for the dressing; season with salt and black pepper.
5Combine black raisins and golden raisins in a small bowl.
6Place 3 to 4 slices pear, apple, and Asian pear in fan-shape on each lettuce leaf.
7Sprinkle raisins and walnuts, and drizzle dressing over fruit slices.