1 tsp sugar
1 tbsp fresh lime juice
1 tbsp mirin (sweet Japanese rice wine)
1 tbsp soy sauce
1 tbsp unseasoned rice vinegar
60g thin rice noodles
12 8-inch rice paper rounds
150g halved little gem lettuce leaves
250g shredded rotisserie chicken
1 red bell pepper, thinly sliced into 2-inch matchsticks
1 medium carrot, very thinly sliced into 2-inch matchsticks
1 English cucumber, thinly sliced into 2-inch matchsticks
1 red chile (such as Fresno; optional)
25g cilantro leaves with tender stems
25g mint leaves
Stir sugar and 1 Tbsp. warm water in a small bowl to dissolve sugar. Stir in lime juice, mirin, soy sauce, and vinegar; set dipping sauce aside.
Soften rice noodles according to package instructions. Drain; run under cold water until chilled.
Fill a shallow dish with warm water. Working with 1 rice paper round at a time, dip in water, turning occasionally, until just pliable but not limp, about 20 seconds (replenish with more warm water as needed). Transfer to a cutting board.
Place a ½ lettuce leaf in center of the rice paper. Top with a small handful of rice noodles and a few pieces each of chicken, bell pepper, carrot and cucumber. Top with chile, if using, and cilantro and mint. Fold bottom of rice paper over filling, then fold in sides and roll like a burrito into a tight cylinder; cut in half if desired. Place roll, seam side down, on a platter. Repeat to make 11 more rolls. Serve with reserved dipping sauce.