01 - Combine ground pork, minced garlic, sugar, fish sauce, oyster sauce, cornstarch, black pepper, and oil in a large bowl. Mix thoroughly until the mixture becomes sticky and well combined.
02 - Wet your hands with water to prevent sticking. Shape the pork mixture into 8 uniform sausage-shaped logs, approximately 4 inches long each.
03 - Preheat a grill pan or outdoor grill over medium-high heat. Grill the pork sausages for 10-12 minutes, turning occasionally until golden brown and cooked through. Set aside to rest.
04 - Whisk together fish sauce, lime juice, sugar, and water in a small bowl until completely dissolved. Stir in minced garlic and sliced chili. Adjust sweetness or acidity to personal preference.
05 - Rinse and thoroughly dry lettuce, mint, and cilantro. Julienne the cucumber and carrot into thin, matchstick strips. Set aside separate piles for assembly.
06 - Fill a large shallow dish with warm water. Dip a rice paper wrapper into the water for 5-7 seconds until just pliable but not soggy. Lay flat on a clean, damp kitchen towel.
07 - Place a lettuce leaf on the lower third of the wrapper. Top with a small bundle of vermicelli, julienned cucumber and carrot, and fresh mint and cilantro leaves. Position one grilled pork sausage on top. Fold both sides inward, then roll tightly from bottom to top to enclose the filling completely.
08 - Repeat the assembly process with remaining ingredients to create 8 spring rolls. Serve immediately with the prepared Nuoc Cham dipping sauce on the side.