This salad is a beautiful study of contrasting flavors, textures and colors, with a mango-based dressing that gives the dish an Asian twist to unite all of the various ingredients perfectly.
The dressing can be made up to 5 days in advance, so you can assemble this composed salad just before serving.
To make the dressing, place one quarter of the mango (1/2 cup) in a food processor or blender and add the oil, vinegar, fish sauce, lime zest and juice, and chili sauce. Process until very smooth. Set aside at room temperature if you plan to serve the salad within an hour or two; otherwise, cover and refrigerate for up to 5 days. The recipe makes about 2/3 cup of dressing.
Place the remaining mango, shrimp, avocado, peas, tomatoes, mint, basil and green onions in a large bowl. Add about 1/4 cup of the dressing and toss gently to coat. Place the lettuce leaves in another bowl and drizzle with enough dressing to coat the greens.
Arrange the lettuce on a large platter or divide among 4 plates. Arrange the shrimp mixture atop the greens and serve immediately.