FOR THE DIPPING SAUCE:
4 tablespoons Demerara or granulated light brown sugar
3 tablespoons rice vinegar
4 tablespoons lime juice, from 2 large limes
4 tablespoons best quality fish sauce, such as Red Boat
2 garlic cloves, minced
1 1-inch length ginger, peeled and minced
1 hot red or green bird chile, thinly sliced
FOR THE STIR-FRY:
12 ounces rice vermicelli noodles
1 pound beef skirt steak or sirloin, in thin 1/4-inch slices
2 tablespoons best quality fish sauce, such as Red Boat
1 tablespoon Demerara or granulated light brown sugar
3 garlic cloves, minced
3 tablespoons finely chopped lemon grass, tender centers only
1 head lettuce, such as butter lettuce or Little Gems, tender center leaves separated
2 tablespoons vegetable oil
4 scallions, slivered
1 medium carrot, cut in 3-inch lengths, julienned (about 1 cup)
1 small cucumber, 3-inch lengths, julienned (about 1 cup)
1 3-inch length daikon radish, julienned (about 1 cup)
Mixture of cilantro sprigs, mint leaves, basil leaves and small perilla (shiso) leaves, about 3 cups
4 tablespoons crushed roasted peanuts
4 tablespoons fried shallots, available in Asian groceries (or make your own using this recipe)
Small handful bean sprouts or sunflower sprouts (optional)
MAKE THE DIPPING SAUCE:
In a small bowl combine sugar, rice vinegar and lime juice and stir to dissolve. Add fish sauce, garlic, ginger, chiles and 1/2 cup water and stir together. Let sit for 15 minutes for flavors to meld. (May be prepared a day ahead and refrigerated.)
Bring a large pot of water to the boil. Add rice noodles, stir and turn off heat. Let noodles soften (5 to 8 minutes, depending on brand), then drain and rinse with cold water. Leave in colander at room temperature.
Meanwhile, combine beef, fish sauce, sugar, garlic and lemon grass in a bowl. Massage seasoning into beef and let sit for 15 minutes.
Line a serving bowl or four individual large wide soup bowls with a few lettuce leaves and top with noodles.
Heat the oil in a wok over high heat. When wok is nearly smoking, add beef and quickly stir-fry until lightly browned and just cooked, about 2 minutes. Work in batches if necessary so meat browns and doesn’t steam. (If you do not have a wok, you may use a cast iron skillet and work in batches.)
Top noodles with cooked beef, scallions, carrot, cucumber and daikon. Sprinkle with herbs, crushed peanuts and fried shallots (add sprouts if using). Drizzle lightly with dipping sauce and pass remaining sauce at table.