Bring a medium pot of water to a rolling boil. Add the 60 g dry rice vermicelli and cook according to package instructions (usually 2–3 minutes) until just tender. Cooking until al dente prevents the noodles from turning mushy later; rice vermicelli always continues to hydrate slightly after draining.

As soon as the noodles are tender, drain them and rinse thoroughly under cold running water, then transfer to a bowl of ice water for 30–60 seconds to stop the cooking immediately and cool them. Shocking the noodles preserves a springy texture and prevents them from clumping.

Drain the noodles well, then toss gently with a tiny pinch of salt and 1/2 teaspoon neutral oil to prevent sticking. Set aside in a single layer or loosely coiled into a serving bowl; this keeps them separate and makes plating easier.

While the noodles cook, season the 120 g thin-sliced flank steak lightly with a pinch of salt and a few grinds of black pepper. Let the beef sit at room temperature for 5–10 minutes—this brings it closer to even cooking temperature so the outside won’t overcook before the center is warm.

Heat a heavy skillet or cast-iron pan over high heat until smoking-hot. Add 1 teaspoon neutral oil and spread to coat. A very hot pan is essential for a fast sear that creates a deeply browned crust (Maillard reaction) without overcooking the interior.

Quick-sear the thin slices of flank steak in the hot pan: lay them in a single layer (do not overcrowd), sear 30–45 seconds per side for medium-rare to medium depending on thickness. Thin slices cook fast — short searing time gives a savory crust while keeping the meat tender. Transfer to a cutting board and let rest 3–5 minutes so juices redistribute.

Slice the rested beef thinly against the grain. Cutting against the grain shortens muscle fibers and makes each bite easier to chew and more tender—especially important for flank steak.

Make the dressing (nuoc cham-inspired): whisk together 1 tbsp fish sauce, 1 tbsp fresh lime juice, 1 tsp sugar (or palm sugar), 1 minced garlic clove and optional 1/2 tsp minced chili. If the dressing tastes very salty, add 1–2 tsp of warm water to round it out. Taste and adjust — the goal is a lively balance of salty, sour and a hint of sweet.

Prep the vegetables and herbs: thinly slice the 1/4 cucumber, shred the 1/4 cup carrot, pick whole or tear the mint and cilantro leaves from stems. Dry herbs on a paper towel if they’re wet—excess water dilutes the dressing and makes the salad soggy.

Assemble: place the drained vermicelli in a shallow serving bowl. Arrange shredded carrot and cucumber on top, scatter the herb leaves, and fan the sliced beef over the noodles. Building the salad in layers keeps the textures distinct until serving.

Just before serving, pour the dressing evenly over the salad (use as much as you like—about half to a full batch recommended for this portion), then sprinkle 1 tbsp crushed roasted peanuts on top. Toss lightly at the table or serve composed so guests can mix their own. Adding the dressing last preserves the crispness of the vegetables and the crunch of the peanuts.

Serve immediately. If you must hold the dish for a short time (10–15 minutes), keep the dressing separate and dress just before eating to avoid sogginess.