The sugar cane in this recipe isn't merely there to serve as a handle for the minced shrimp and pork; it also keeps the mixture moist from within and adds a subtle sweetness. Look for sugar cane in markets that serve Asian and Mexican communities. If possible, buy the cane cut into shorter, thinner lengths (about 6-8cm long), because it's difficult to cut yourself.
You can still make this dish if you don't have sugar cane (although you'll have to call it something else) - just form the mixture into flattish discs with an indentation at the centre, then fry as directed in the recipe.
Make a shallow cut along the back of the shrimp and pull out and discard the vein. Cut the shrimp into small pieces.
Roughly chop the garlic. Cut the spring onions into thin rounds.
Put the shrimp in the bowl of a food processor and add the pork, garlic, spring onions, 20ml (4 tsp) fish sauce, 5 grams (1 tsp) of granulated sugar and the salt. Process until the shrimp pieces are very finely chopped, but not a smooth paste. Transfer the ingredients to a mixing bowl.
Whisk the egg white until frothy, then add it to the bowl. Stir vigorously in one direction for about a minute, or until you see protein strands developing in the mixture.
Heat a small skillet and pan-fry a little of the mixture. Taste it to see if the seasonings are right, and correct, if necessary. Cover the bowl with clingfilm and refrigerate for at least an hour.
While the mixture is chilling, make the sauce. Mince the garlic, and cut the bird's-eye chilli into thin rounds, shaking out and discarding the seeds as you go.
Mix the fish sauce with the lime juice and sugar and stir until the sugar is dissolved. Add the bottled water, then taste, mixing in more lime juice and sugar, if necessary. Stir in the garlic and chilli.
Shape some of the shrimp and pork mixture into a thickness of about 1cm (⅜ in) around the lower two-thirds of each piece of sugar cane, leaving a "handle" of 2-3cm (¾-1¼ in) long.
Pour oil in a wok to a depth of about 6cm (2½ in) and heat it to 170° C (340° F). Fry the sugar cane pieces in batches, turning them over in the hot oil until done, about three minutes.
Drain them on paper towels then place on a serving platter. Arrange the lettuce leaves and herbs on a plate and serve with the dipping sauce on the side.