Cook the shrimp in boiling water until they turn pink and opaque, about 2-3 minutes. Slice each shrimp in half lengthwise and set aside.
Cook the pork belly or loin in boiling water until fully cooked, about 20-30 minutes. Let it cool, then thinly slice and set aside.
Cook the rice vermicelli noodles according to the package instructions. Drain and rinse under cold water to stop the cooking process.
In a small saucepan, combine the hoisin sauce, peanut butter, water, soy sauce, sugar, minced garlic, and chili garlic sauce (if using).
Cook over medium heat, stirring constantly, until the sauce is smooth and slightly thickened, about 5 minutes.
Remove from heat and set aside. Garnish with crushed peanuts before serving.
Fill a large bowl with warm water.
Dip one rice paper wrapper into the warm water for about 5 seconds, or until it becomes pliable. Remove and lay it flat on a clean surface.
In the center of the wrapper, place a few pieces of shrimp, pork slices, a small handful of rice vermicelli noodles, lettuce leaves, fresh herbs, shredded carrots, and julienned cucumber.
Fold the bottom of the wrapper over the filling, then fold in the sides and roll tightly to enclose the filling. Repeat with the remaining ingredients and wrappers.
Enjoy your meal!