Fresh Spring Rolls

Whisk ⅔ cup hoisin sauce, ⅓ cup creamy peanut butter, 3 Tbsp. fresh lime juice, 1½ Tbsp. soy sauce, and ⅓ cup water in a small bowl until smooth. Set aside. Do ahead: Peanut sauce can be made 1 day ahead; refrigerate in an airtight container. Bring to room temperature before serving.

Whisk 3 Tbsp. fish sauce such as Thai nam pla or Vietnamese nuoc mam, 3 Tbsp. fresh lime juice, 2½ tsp. (packed) brown sugar in another small bowl until sugar is dissolved. Add 2 Tbsp. water and whisk to combine. Set aside. Do ahead: Nuoc cham can be made 4 hours ahead. Store at room temperature.

Place 12 large shell-on shrimp (21–25 per lb.), peeled, in a 4- to 5-qt. pot of boiling salted water, then reduce heat to medium-low. Poach shrimp at a bare simmer, uncovered, until just cooked through, about 3 minutes. Using a slotted spoon, transfer shrimp to a bowl of ice-cold water to stop cooking (reserve cooking water). Chill shrimp in ice bath until cold, about 2 minutes, then drain and pat dry. Cut each shrimp in half lengthwise, deveining if necessary.

Return shrimp cooking water to a boil and add 3 oz. rice vermicelli noodles; cook until just tender, about 3 minutes. Drain in a colander, then rinse under cold running water and drain well. Stir 3 Tbsp. rice vinegar, 2 Tbsp. granulated sugar, and ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt in a large bowl until sugar is dissolved; add noodles and toss to coat.

Put 2 layers of paper towels on a work surface and fill a shallow baking pan with warm water. Check 8 (8") rice-paper rounds, plus more in case some tear and use only those that have no holes. Soak 1 round in warm water until pliable, 30 seconds to 1 minute, then carefully transfer to paper towels.

Arrange 3 shrimp halves (cut sides up) in a row across bottom third (part nearest you) of soaked rice paper. Spread ¼ cup noodles on top of shrimp and arrange 3 fresh cilantro leaves, 3 fresh mint leaves, 8 seedless cucumber matchsticks, six 3"-long scallion strips, and 10 firm-ripe mango matchsticks horizontally on top of noodles. Fold bottom of rice paper over filling and begin rolling up tightly, stopping at halfway point. Arrange 3 more fresh mint leaves and 3 more fresh cilantro leaves along crease, then fold in ends and continue rolling. Transfer rice paper roll, seam side down, to a plate and cover with dampened paper towels. Repeat to make 7 more spring rolls. Serve, whole or halved diagonally, with nuoc cham and peanut dipping sauce. Do ahead: Spring rolls can be made 4 hours ahead and chilled, covered with dampened paper towels, and then with plastic wrap. Bring to room temperature before serving.