Preparation Freeze beef 30 minutes. Using large knife, thinly slice beef crosswise. Mix meat, lemongrass, 3 tablespoons fish sauce, soy sauce, 3/4 teaspoon sugar, and garlic in large bowl. Sprinkle generously with black pepper. Let stand at room temperature 30 minutes or chill up to 3 hours. Whisk 3 tablespoons oil, lime juice, shallot, chili, 1 tablespoon fish sauce, and 3/4 teaspoon sugar in bowl to blend. Season dressing with salt and pepper. Let stand at room temperature 30 minutes. Place mustard greens, bok choy, onions, and basil in large bowl. Add 3/4 of dressing; toss to coat. Season salad with salt and pepper. Heat 1 tablespoon oil in heavy large skillet over high heat. Working in 2 batches, stir-fry meat until cooked to desired doneness, about 35 seconds for rare. Add to greens. Add remaining dressing and toss to combine. Serve immediately. *Available at Asian markets and in the Asian foods section of many supermarkets. **Opal basil has purple leaves and a milder flavor than sweet basil. It is available at Asian markets and some supermarkets.
Preparation Freeze beef 30 minutes. Using large knife, thinly slice beef crosswise. Mix meat, lemongrass, 3 tablespoons fish sauce, soy sauce, 3/4 teaspoon sugar, and garlic in large bowl. Sprinkle generously with black pepper. Let stand at room temperature 30 minutes or chill up to 3 hours. Whisk 3 tablespoons oil, lime juice, shallot, chili, 1 tablespoon fish sauce, and 3/4 teaspoon sugar in bowl to blend. Season dressing with salt and pepper. Let stand at room temperature 30 minutes. Place mustard greens, bok choy, onions, and basil in large bowl. Add 3/4 of dressing; toss to coat. Season salad with salt and pepper. Heat 1 tablespoon oil in heavy large skillet over high heat. Working in 2 batches, stir-fry meat until cooked to desired doneness, about 35 seconds for rare. Add to greens. Add remaining dressing and toss to combine. Serve immediately. *Available at Asian markets and in the Asian foods section of many supermarkets. **Opal basil has purple leaves and a milder flavor than sweet basil. It is available at Asian markets and some supermarkets.