For the Dipping Sauce: In a medium bowl, combine ½ cup (120ml) warm water with the sugar, fish sauce, and lime juice and mix until sugar has fully dissolved. Stir in garlic and chile, if using, and set aside.

For the Filling: Using your hands, squeeze jicama to remove excess liquid. Spread jicama and carrot in an even layer on a paper towel-lined rimmed baking sheet and let air-dry for 1 hour.

In a small bowl, soak cellophane noodles in 2 cups (475ml) warm water for 15 minutes. Drain softened noodles, squeeze noodles dry to remove excess liquid, then cut into roughly 1-inch strands. Return to now-empty bowl and set aside.

In a separate small bowl, soak wood ear mushrooms in 1 cup (235ml) warm water for 15 minutes. Drain and rinse thoroughly. Chop fine, discarding any tough stems.

In a large bowl, combine prawns, pork, carrot, jicama, cellophane noodles, wood ear mushrooms, shallot, scallion, garlic, sugar, salt, and pepper. Using your hands, mix until fully combined. To check for seasoning, cook 1 tablespoon of the filling in a small pan over medium heat or microwave on a plate for 45 seconds before tasting for seasoning. Adjust uncooked filling to taste with extra sugar or salt if needed.

To Form and Fry: In a large shallow wide bowl, stir together 1 ½ cups (355ml) warm water with the soda. Working with one rice paper wrapper at a time, dip into the liquid until the wrapper is just pliable. Remove and shake off excess water. Lay moistened wrapper on a clean counter or cutting board. Place ¼ cup filling just below center of rice paper sheet. Using hands, shape filling into a 4 ½- to 5-inch log parallel to counter edge.

Fold the left and right sides of the wrapper towards the center to enclose filling snugly. Fold bottom corner of wrapper over filling and press gently along length of filling to remove air pockets. Starting at bottom counter edge, gently wrap up and over the filling to form a tight cylinder and finish rolling to seal. Transfer roll seam side down to a rimmed baking sheet. (Do not stack). Repeat with remaining wrappers and filling; you should have about 14 rolls. Cover filled rolls with a damp towel and refrigerate rolls until ready to fry.

Set wire rack in rimmed baking sheet. Line rack with a double layer of paper towels. In a large Dutch oven, heat oil over medium-high heat to 350°F (175°C). Working with 1 at a time, use tongs or spider skimmer to gently transfer 6 rolls to oil and fry rolls until golden brown all over and crispy, 8 to 10 minutes, turning rolls and gently separating rolls with tongs halfway through frying. Adjust burner as needed, to maintain oil temperature of 325℉ to 350℉ ( 160 to 175℃) degrees. Transfer fried rolls to prepared rack. Repeat with remaining rolls, frying 6 to 4 at a time. Let cool for 5 minutes before serving.

For Serving: Serve imperial rolls with lettuce, fresh herbs, dipping sauce, pickled daikon and carrots, and pickled leeks, if using, alongside dipping sauce. To eat, wrap each roll in a lettuce leaf, top with herbs and pickles, and dip into sauce.