How to Make It
In a large skillet, heat 1 tablespoon of vegetable oil. Add the shallot and cook over moderate heat until softened, about 2 minutes. Add the cabbage and cook, stirring a few times, until just wilted, about 3 minutes. Add 1/2 tablespoon each of the fish sauce and sugar and cook, stirring, for 1 minute. Transfer the cabbage to a large bowl.
Add 1/2 tablespoon of oil to the skillet. Add the pork and cook over moderately high heat, breaking up the meat with a wooden spoon, until no trace of pink remains, about 3 minutes. Season with salt. Using a slotted spoon, add the pork to the cabbage. Add the shrimp to the skillet and stir-fry for 1 minute. Add the remaining 2 1/2 tablespoons of fish sauce and 1 tablespoon of sugar and cook, stirring to dissolve the sugar. Scrape the shrimp into the bowl of cabbage.
Set a steamer basket in a medium saucepan with 1/2 inch of water and bring to a boil. Add the potato matchsticks, cover and steam until just tender, about 2 minutes. Let cool, then add to the bowl. Mix well. Stir in the egg and ground pepper and mix again.
Fill a shallow bowl with water. Working with 2 rice papers at a time and using your palm, rub the rice papers on both sides with water. Let the papers stand for about 1 minute, until softened; do not over-moisten or the papers may tear. Place a rounded tablespoon of the filling on the lower third of each rice paper and bring the bottom up and over the filling. Press tightly to enclose the filling and roll up, folding in the sides as you go. The rolls should seal themselves; if not, moisten with a little water. Place the rolls on a platter seam side down and repeat with the remaining rice papers and filling.
Combine all of the ingredients in a bowl and mix well.
Preheat the oven to 375°. In a medium saucepan, heat 1 1/2 inches of vegetable oil to 320° over moderately high heat. Fry 4 to 5 rolls at a time, stirring occasionally to keep them from sticking together, until they’re crisp but still white, about 6 minutes. Keep the oil between 320° and 350° during frying. Transfer the rolls to a rack set over a large baking sheet to drain. When all of the rolls have been fried, transfer them to a baking sheet. Warm them in the oven for 2 minutes. Serve the rolls right away with the dipping sauce.
The filling and dipping sauce can be refrigerated overnight. Bring to room temperature before using.
Rice papers are available online or at Asian markets.