One bunch of fresh mint, leaves picked off and washed
1/2 cup chopped peanuts, toasted in a dry pan for 3–4 minutes
To make the beef marinade: Remove and discard the outer layer of each piece of lemongrass. Trim about 3-inches of the dry, stick-like part of the lemongrass from the top so that you are left with the plumper, white interior. Slice this interior into small coins, and then finely chop those coins until evenly minced. Place minced lemongrass in a medium bowl. Peel and mince the garlic and add to the bowl with the lemongrass. Add the sugar, salt, soy sauce, sesame oil and canola oil to the bowl and stir to combine. Add the sliced flank steak and stir to coat with the marinade. Cover with plastic wrap and refrigerate for at least 4 hours.
To make the pickled carrots: Use a julienne peeler to shred the carrots into long, noodle-like strips. If you don’t have a julienne peeler, carefully chop the carrots into long, thin match-sticks. Place the carrots in a heatproof bowl. Add the vinegar, sugar, water, and star anise to a small saucepan. Bring to a simmer over medium heat, stirring to dissolve the sugar. Simmer just for 30 seconds, then pour the hot liquid over the carrots. Cover with plastic wrap and refrigerate until ready to use, at least an hour. Discard the star anise before serving.
To make the nuoc cham: Place all of the ingredients in a medium bowl. Stir until the sugar is dissolved. Taste and adjust seasoning if desired.
To finish and assemble the bowls: Cook the rice noodles according to the package directions. Drain and rinse.
Just before serving, cook the beef. Heat the canola oil in a large, heavy-bottomed frying pan over medium-high heat. When the pan is hot, add the marinated beef to the pan in batches (each batch of beef should easily fit in the pan in a single layer). Cook the beef for 1-2 minutes on each side, until deeply caramelized on the outside but just tender in the center. Remove to a plate and continue until you have cooked all the beef.
To serve, fill each bowl halfway with rice noodles. Top with a quarter of the pickled carrots, several pieces of the cooked beef, a small handful of fresh mint leaves, and 2 tablespoons of chopped peanuts. Serve the bowls with the nuoc cham sauce on the side, so that each person can dress their bowl according to taste.
If you pickle the carrots at the same time that you marinate the beef, this will only take about 20 minutes to finish up before serving.