True Buddhist vegetarians would not use garlic or fish sauce and would limit the dips to plain soy or plum sauce. Unless you are in this category, Peanut Sauce (Nuoc Leo) and Nuoc Cham are great dips as well.
Prepare the Vegetable Platter, noodles and dipping sauce. Set aside.
Soak the noodles in warm water and the mushrooms in hot water for 30 minutes; drain. Cut the noodles into 1/2-inch lengths. Remove and discard the stems from the mushrooms; squeeze to extract most of the soaking liquid. Mince all of the mushrooms.
Combine all of the filling ingredients in a large mixing bowl; blend well with your hands. Set aside.
Assemble the rolls: Fill a large bowl with 4 cups of warm water and dissolve the sugar in it.
Rice paper is quite fragile. Work with only 4 sheets at a time, keeping the remaining sheets covered with a barely damp cloth to prevent curling.
Immerse the rice paper, one sheet at a time, into the sweetened warm water. Quickly withdraw it and lay it flat on a dry towel. Do this with 4 sheets without letting them touch each other. The rice paper will become pliable within seconds.
Fold over the bottom third of each round. Put 1 generous teaspoon of filling in the center of the folded-over portion. Press it into a compact rectangle. Fold one side of the paper over the mixture, then the other side. Roll from the bottom to the top to completely enclose the filling. Continue until all of the mixture is used. (The rolls can be prepared 1 day in advance. Wrap and refrigerate.)
Fry the rolls: If possible use 2 skillets. Pour 1 to 1 1/2 inches of oil into each skillet and heat to 325F. Working in batches, add some of the rolls without letting them touch, or they will stick together. Fry for 10 to 12 minutes, turning often, until golden and crisp. Remove the rolls from the oil with tongs and drain on paper towels. Keep warm in a low oven until all of the rolls are cooked.
To serve, each diner wraps a roll in a lettuce leaf along with some noodles and selected items from the Vegetable Platter and dips the package in the dipping sauce.
NOTE: The fried rolls can be frozen, then thawed and reheated in a 350F oven just to crisp and heat through.