In a large bowl, combine the ground pork, chopped shrimp, shredded taro, vermicelli, wood ear mushrooms, shiitake mushrooms, onion, garlic, fish sauce, sugar, and black pepper. Mix with your hands until evenly combined, then let it rest 15 minutes so the flavors meld.
Fill a wide shallow bowl with warm water. Dip one rice paper sheet for 2 to 3 seconds, shake off the excess, and lay it flat on a clean damp towel. The sheet will continue to soften as you work.
Place about 3 tablespoons of filling in a log just below the center of the rice paper. Fold the bottom edge over the filling, fold in the sides, and roll snugly (not tightly) into a cylinder. Place seam-side down on a tray. Repeat with the remaining rice paper and filling.
Let the rolled cha gio rest, uncovered, for 10 minutes. This dries the seams and keeps them from bursting in the fryer.
Pour oil into a wok or deep heavy pot to a depth of 2 inches and heat to 350F (175C). Line a wire rack over a baking sheet.
Add rolls to the oil in batches of 5 to 6, leaving space between them. Fry 7 to 9 minutes, turning once or twice, until deep golden, blistered, and crisp. Lift out with a slotted spoon and drain on the wire rack.
While the first batch fries, dissolve the sugar in the warm water, then stir in the fish sauce, lime juice, garlic, and chile. Taste and adjust - it should be bright, punchy, and balanced.
Pile the cha gio on a platter with lettuce leaves and fresh herbs. Serve with the nuoc cham for dipping. Eat within 15 minutes of frying for maximum crunch.