Heat 1 tablespoon of the oil in a large nonstick pan over moderate heat. In a bowl, combine the eggs and a pinch of salt and beat well. When the pan is hot, pour in half the beaten eggs and quickly swirl to cover the bottom of the pan. Cook until firm, about 1 minute. Flip the egg crepe and cook another minute. Transfer the crepe to a plate. Repeat with the remaining egg batter. When the crepes are cool enough to handle, cut into thin strips and set aside.
Heat the remaining 3 tablespoons of oil in a large pan over high heat. Add the shallot and stir until fragrant, about 1 minute. Add the soy sauce, jicama, carrot, water and the remaining salt. Cook, uncovered, until the vegetables are soft, about 15 to 20 minutes. Transfer the vegetables to a dish.
Combine the hoisin sauce and chili paste in a small bowl and set aside. Set up a workstation by placing the ingredients in the order in which they will be needed: rice papers, egg strips, lettuce, jicama mixture, tofu, hoisin mixture, basil, peanuts.
Fill a large bowl with hot water. Cover a cutting board with a damp towel and place it next to the bowl. Working with 2 rice paper rounds at a time, dip one, edge first, into the hot water and turn to wet it completely, about 10 seconds. Lay the round down on the towel. Repeat with the other round and place it next to the first. (This allows you to work with one while the second rests.)
Neatly place on the bottom third of the first round a few strips of egg crepe, 1 piece of lettuce, 2 tablespoons jicama mixture (no juice), 2 pieces of tofu, 1/2 teaspoon hoisin sauce mix, 2 or 3 basil leaves and a sprinkling of peanuts. Make sure the filling is neatly stacked. Fold the bottom edge over the filling, tuck in the sides, and roll into a cylinder. A perfect bo bia is about 1 inch wide and 4 inches long. Repeat with the remaining ingredients. Serve the rolls whole or cut in half.
Recipe courtesy of Mai Pham, Mai Pham's Pleasures of the Vietnamese Table (HarperCollins, 2001)