In a small saucepan over medium heat, combine rice wine vinegar and granulated sugar. Stir continuously for 2-3 minutes until the sugar fully dissolves. Remove from heat and allow it to cool for about 10 minutes. Once cooled, mix in sambal, minced cilantro, chopped serrano pepper, minced garlic, and grated fresh ginger.

Heat a tablespoon of vegetable oil in a skillet over medium-high heat. Add shiitake mushrooms and sauté for 3-4 minutes, or until they are tender and slightly caramelized. Stir in tamari and light brown sugar, coating the mushrooms evenly, and cook for an additional 1-2 minutes while stirring.

Fill a shallow dish with warm water. One by one, dip each rice paper wrapper into the water for about 10 seconds until softened but not too mushy. Carefully lift the wrapper out and lay it flat on a clean surface.

On the center of the softened rice paper, layer a butter lettuce leaf, a handful of shredded purple cabbage, a few matchstick carrots, and slices of red and yellow bell peppers. Spoon in some sautéed shiitake mushrooms and several mint leaves.

Starting from the edge closest to you, fold the rice paper over the fillings, tucking it tightly. Fold the sides inward, then continue rolling away from you until the entire spring roll is secure.

Using a sharp knife, cut each spring roll in half diagonally for an appealing presentation. Arrange the spring rolls on a platter alongside your prepared dipping sauce.