Place rice vermicelli in a large heatproof bowl. Pour boiling water over noodles to cover by about 1 inch and let sit 4–5 minutes until tender but not mushy. Drain and rinse under cold running water until cool. Toss gently to separate and set aside.

Prepare vegetables and herbs

Julienne carrots and peeled cucumber (remove seeds if very watery). Tear leafy greens into pieces slightly narrower than the rice paper wrapper. Pick mint and cilantro leaves from stems. If using avocado, slice thinly. Have bean sprouts rinsed and drained.

Set up rolling station

Fill a large shallow bowl or pie plate with warm water for softening rice papers. Lay a clean damp kitchen towel or cutting board nearby for assembling rolls. Arrange fillings in small piles so they are easy to reach.

Soften rice paper

Working one at a time, dip one rice paper wrapper into the warm water for about 8–12 seconds — lift and let excess water drip off. Place the softened wrapper on the damp towel or board with one edge closest to you.

Assemble roll

Brush a thin film of softened sesame oil across the center of the wrapper to prevent sticking (optional). In a line across the lower third of the wrapper (closest to you), place: a small handful (about 2 tablespoons) of vermicelli, 2–3 strips of carrot, 2–3 strips of cucumber, a small handful (about 1/6 cup) of torn greens, 4–6 herb leaves, a small pinch of bean sprouts, and a slice or two of avocado if using. Don’t overfill — leave margins to fold.

Roll and seal

Fold the bottom edge up over the fillings, then fold the sides in toward the center, and continue rolling away from you tightly but gently until sealed. Place the finished roll seam-side down on a platter. Repeat with remaining wrappers and fillings. If rolls stick together, separate with parchment or wax paper.

Storage and serving

Cover rolls loosely with a damp paper towel and plastic wrap if not serving immediately to keep them from drying out. Serve within 2–4 hours for best texture (rice papers become chewier over time).

Peanut Dipping Sauce

In a small bowl, combine peanut butter, soy sauce, rice vinegar, honey (or maple), minced garlic, lime juice, sesame oil, and red pepper flakes if using.

Whisk in warm water, 1 tablespoon at a time, until sauce reaches a smooth, dippable consistency (about 2–3 tablespoons total). Taste and adjust seasoning: more soy for salt, more lime or vinegar for acidity, more honey for sweetness, or a pinch of water to thin.

Transfer sauce to a small serving bowl and sprinkle a few red pepper flakes or chopped peanuts on top if desired.