In a pan or wok over medium heat, cook onions and garlic for 3-4 minutes, or until fragrant.
Add the ground pork and cook until browned, breaking it into small pieces.
Stir in the rehydrated and chopped mushrooms (shitake and wood ear), along with the water chestnuts.
Season with fish sauce, chicken bouillon powder, salt, sugar and black pepper. Remove the pan or wok from heat and set aside.
Assemble:
Prepare a large plate and brush it lightly with neutral oil to prevent sticking.
Soak each rice paper sheet in lukewarm water for about 3 minutes.
Gently lay the softened rice paper on the oiled plate. Place a spoonful of the prepared filling in the center of each rice paper sheet. Fold the sides over the filling and roll tightly to enclose the filling completely. Repeat with the remaining rice paper sheets and filling.
Serve:
Serve with a side of thinly sliced cucumbers, bean sprouts (blanched), fresh herbs (eg. mint, basil, cilantro).
Top it with fried shallots and dip into nước mắm.
Notes
For the nước mắm, combine and mix ¾ cup of water with 4 tbsp white granulated sugar, 4 tbsp freshly squeezed lemon, 6 tbsp fish sauce and 2 cloves of garlic (minced).