Bring a large saucepan of water to a boil. Drop in the snow peas and cook only until they turn bright green, about 45 seconds. Turn them into a colander and run briefly under cold water to stop the cooking. Drain well and set aside.
Cut cucumber, onion, and half the mango into small, more or less uniform dice. You should have about 1 cup of cucumber, ¾ cup onion, and ½ cup mango.
Dressing: 2 tablespoons each of corn oil, olive oil, and rice vinegar 1 tablespoon tamari or other aged soy sauce ¼ teaspoon vanilla extract ½ teaspoon salt, or to taste
Whisk dressing ingredients together until emulsified.
Put the rice in a large bowl and stir in the dressing. Shred about two-thirds of the snow peas and ad them, along with all of the diced cucumber, onion, and mango, and about two-thirds of the lobster. Taste the salad and add salt if desired.
Slice the remaining half of the mango. Line 4 salad plates with lettuce leaves. Divide the salad among the plates and garnish with the remaining lobster, snow peas, and sliced mango.