Make the sauce: Grind the peanuts in a food processor. Heat the vegetable oil in a saucepan over medium heat. Add the curry paste and cook 1 minute. Add the fish sauce and cook 1 more minute. Add the ground peanuts and cook, stirring, about 4 minutes. Sprinkle in the sugar and cook 1 to 2 more minutes. Stir in the coconut milk, chicken broth and hoisin sauce. Reduce the heat to low and simmer until thick, about 20 minutes. Let cool.
Make the rolls: Fill a saucepan with water and season with salt. Add the vinegar, sugar and peppercorns and bring to a boil over high heat. Add the shrimp and simmer until pink, 2 minutes. Drain and run under cold water. Peel the shrimp, then halve lengthwise and devein. Cover and chill.
Cook the rice noodles as the label directs, then drain. Cut the cucumber and scallions into matchsticks and toss with 1 teaspoon salt in a bowl. One at a time, soak a rice paper wrapper in warm water until pliable, 30 seconds, then lay on a cutting board and pat dry. Arrange 3 shrimp halves across the middle of the wrapper; top with some noodles, herbs, cucumber, scallions and lettuce. Fold the bottom of the wrapper over the filling, then fold in the sides and roll up into a tight bundle. Cut in half; serve with the peanut sauce.