To make the dipping sauce: combine the first 6ingredients in a small bowl and season, to taste, with red pepper flakes. Set aside.
To make the rolls: in a large bowl combine the bean thread noodles, cabbage, carrots, green onion, and sesame seeds. Place the cilantro, mint and shrimp in separate work bowls nearby.
To soften the rice paper, fill a pie plate or shallow baking dish with tepid water. Place 2 or 3 rice paper sheets in the water and allow to soak about 45 seconds to 1 minute. Remove 1 at a time and carefully stack between sheets of paper towels. Continue soaking and draining until you have softened 16 rice sheets.
Turn over the stack and begin working from the bottom of the stack first. Place a softened rice paper sheet on a clean work surface. On the bottom third of the sheet, pile 1/4 cup of the noodle mixture. Just above the noodles, place a shrimp half, skin side down, and top with a cilantro leaf and mint leaf. Fold the bottom of the paper up and over the noodle mixture, then fold each side toward the center, rolling gently and as tightly as possible from the bottom until completely rolled. Place rolls seam side down on a plate and continue until all ingredients have been used.
Keep assembled rolls under wet paper towels covered with plastic wrap. Store at room temperature up to 3 hours, do not refrigerate.
Recipe courtesy of Michele Adams and Gia Russo, Wedding Showers, Chronicle Books, 2000