These refreshing salad rolls have wonderful textural appeal from crunchy sprouts, lettuce, and carrot and lightly chewy rice paper. Mint and cilantro give the vegetable mixture bright taste. For a milder dipping sauce, seed the Thai chile pepper. Allow the sauce to stand for about 30 minutes before serving so the flavors can meld.
To prepare rolls, add hot water to a large, shallow dish to a depth of 1 inch. Place 1 rice paper sheet in dish, and let stand for 30 seconds or just until soft. Place sheet on a flat surface. Arrange 1/4 cup lettuce over half of sheet, leaving a 1/2-inch border. Top with 1/4 cup bean threads, 2 tablespoons sprouts, 2 tablespoons carrot, 1 tablespoon mint, 1 tablespoon cilantro leaves, and 1 1/2 teaspoons green onions. Folding sides of sheet over filling and starting with filled side, roll up jelly-roll fashion. Gently press seam to seal. Place roll, seam side down, on a serving platter (cover to keep from drying). Repeat procedure with remaining roll ingredients.
To prepare sauce, combine sugar and the remaining ingredients in a small bowl, stirring with a whisk until sugar dissolves. Serve sauce with rolls.