In a medium bowl, whisk together 1 cup peanut butter and 1 cup hoisin sauce until smooth. Add 2 tbsp soy sauce, 1 tbsp rice vinegar and 1 tsp sriracha. Gradually whisk in up to 3 tbsp warm water until the sauce reaches a thick but pourable consistency. Taste and adjust: add more soy for salt, vinegar for brightness, or sriracha for heat. Transfer to a serving bowl and set aside.

Set up an assembly station: a shallow wide bowl of warm water (for softening rice papers), a large clean work surface or cutting board, a damp kitchen towel to cover finished rolls, and the dipping sauce within reach.

Vegetables & Herbs

Prepare the vegetables

Peel the carrots and trim ends. Using a julienne peeler or knife, cut carrots into thin matchsticks about 2–3 inches long. Trim cucumber ends, halve lengthwise and scoop seeds if needed, then julienne to match carrot length. Core and thinly slice the red bell pepper into 1/4-inch strips. Thinly shred the red cabbage (aim for fine ribbons). Thinly slice the scallions on a bias into 2-inch pieces. If using butter lettuce, separate leaves and pat dry.

Prepare optional add-ins

If using rice vermicelli, cook according to package until just tender, drain, rinse under cold water and drain well. Slice avocado into 1/4-inch slices just before assembling to avoid browning. Chop roasted peanuts for garnish.

Assembly

Soften rice paper wrapper

Fill a shallow wide bowl or pie dish with warm (not boiling) water. Submerge one rice paper wrapper for 5–8 seconds until it begins to soften but still slightly firm — it will continue to soften on the board. Lift and let excess water drip off briefly.

Place the softened wrapper on the work surface. In the lower third of the wrapper (closest to you) arrange: 1 butter lettuce leaf (optional, helps prevent sogginess), a small handful (about 2 tbsp) of shredded cabbage, a small bundle of julienned carrots and cucumber (about 2–3 tbsp combined), 3–4 thin bell pepper strips, 2–3 mint leaves and a small pinch (~1 tbsp) of cilantro. Add a small amount (about 1/4 cup loosely packed) of cooked vermicelli if using, and 2–3 slices of avocado if desired. Sprinkle a few sliced scallions on top.

Fold the bottom edge of the wrapper up over the filling, then fold in the two sides snugly, and continue rolling away from you to form a tight cylinder. Do not overstuff — leave about 1–1.5 inches of wrapper at the far edge to seal. Place finished roll on a damp towel seam-side down. Repeat with remaining wrappers and fillings.

If not serving immediately, cover the finished rolls with a damp towel and store in a single layer in the refrigerator for up to 6 hours (best within 2–3 hours).

Right before serving, sprinkle toasted sesame seeds and crushed peanuts over the dipping sauce or directly onto the rolls if desired.