01 - Heat a non-stick skillet over medium heat. Add sliced shiitake mushrooms and sauté for 5-6 minutes, stirring occasionally, until tender and lightly browned. Remove from heat and set aside to cool completely.
02 - Slice avocado, julienne carrot and cucumber, thinly slice bell pepper, and chop scallions. Wash spinach or lettuce leaves and pat dry. Arrange all prepared vegetables, herbs, and cooled mushrooms within easy reach for assembly.
03 - Fill a shallow dish with warm water. Dip one rice paper sheet into the water for 10-15 seconds until just pliable and softened. Carefully transfer to a clean, damp kitchen towel or cutting board, laying it flat without folds.
04 - Place a small handful of spinach or lettuce in the center of the rice paper. Layer with avocado slices, sautéed shiitake mushrooms, carrot, cucumber, bell pepper, scallions, cilantro, and mint. Fold the bottom edge over the filling, fold in both sides, then roll tightly from bottom to top to seal. Repeat with remaining ingredients to make 8 rolls.
05 - Whisk together soy sauce, rice vinegar, sesame oil, maple syrup, grated ginger, and minced garlic in a small bowl until smooth and emulsified. Add water 1 teaspoon at a time to reach desired consistency.
06 - Serve spring rolls immediately, either whole or sliced in half diagonally, alongside the dipping sauce. For best texture and flavor, consume within 2 hours of preparation.