Combine the salt and tumeric. Put the eggplant in a colander. Sprinkle with the salt mixture and toss. Set aside for 1 hour. Rinse and pat dry.
Heat some of the oil in a cast-iron skillet. Add the eggplant and cook until golden brown, about 4 minutes per side. Drain on paper towels. Transfer to a large glass or ceramic bowl.
Combine the mustard seeds, vinegar, onion, garlic and gingerroot in a blender or food processor. Puree until smooth. Set aside.
Heat the remaining oil in a clean skillet. Add the mustard mixture and simmer over medium heat for 5 minutes. Add the curry powder, chili, cinnamon, sugar and tamarind. Reduce the heat to medium-low, cover and cook for 15 additional minutes. Pour over the eggplant and marinate in the refrigerator for 4 hours.
Put the steak in a large glass or ceramic baking dish. Combine the garlic, sugar, vinegar, olive oil, nuoc mam, soy sauce and pineapple in a blender or food processor. Puree until smooth. Pour the marinade over the meat. Cover and refrigerate for 2 hours.
Bring the meat to room temperature. Grill over hot Grill over hot coals until rare, about 3 minutes per side. Set aside to rest for 10 minutes.
To assemble, divide the eggplant salad among 4 plates. Slice the meat into very thin strips crosswise. Drape 4 slices of meat over the top of each salad. Garnish with fresh mint.
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