The day before you want to serve, fill a large saucepan with water and bring to the boil. Add the peanuts and simmer for 25 mins. Remove the peanuts, drain and soak overnight in fresh tepid water. Rinse the rice in a sieve under cold running water and leave to soak overnight.
To make the filling, put the dried shiitake mushrooms and dried shrimp in two separate bowls and cover with boiling water. Leave for 15 mins or until completely softened. Remove the mushrooms from the liquid with a slotted spoon and squeeze any excess water back into the bowl. Roughly chop the mushrooms to a similar size as the shrimp. Drain the shrimp and set aside.
Cook the bamboo leaves to make them flexible. Bring a large pan of water to the boil, add the leaves and cook on a high heat for 5 mins. Turn off the heat and keep the leaves in the water for 20 mins. The water should turn a little brown. Rinse and drain the leaves. Drain the rice and peanuts and mix together in a big bowl.
Meanwhile, for the filling, put the diced pork in a pan of boiling water. Simmer for up to 1 hr or until the meat is tender and falls apart easily. Drain and set aside. Heat a large wok on a medium-high heat and add the pork. As some of it is quite fatty, you shouldn’t need to add any more oil, but if it begins to stick, add a little vegetable oil.
Once the pork is browned, add the sliced shallots, shrimp and mushroom. Add the soy sauce and sugar. Cook for a further 1-2 mins until the meat is slightly caramelised. Take the pork off the heat and add the crispy shallots. Using a microplane or box grater, grate the salted egg yolk, if using, into the mixture and mix. Season.
To wrap the bah-tzang, cut around 10 lengths of butcher’s string to around 50cm.
Lay one cooked bamboo leaf on top of another to give a double thickness. Fold the leaves in half and use your hands to form a pointed cone shape. Hold the cone in your hand, point-side down, like a sushi hand-roll or an ice cream cone.
Pack the rice and peanut mix around the outside and the bottom of the leaf-cone to make a layer of rice over the entire surface. Continue until it’s about two-thirds full. Spoon the pork, shrimp and mushroom mixture into the centre of the rice and pack it down tightly. Add another spoonful of rice on top so the filling is completely covered.
To close the bah-tzang, fold the top edge of the bamboo leaves over the rice and tuck it in to seal the gap. Pull the leaves tightly so they enclose the rice and pork, tucking in any loose edges. Use one length of string to secure the parcel, winding it up in the string and leaving a length at the top. Make sure you tie the knots as tightly as possible so none of the filling escapes. Fill the remaining bamboo leaves, and tie them all together.
Bring a large pan of water to the boil, lower in the bah-tzang and cook for 45 mins to 1 hr, then remove them from the water, drain and serve immediately. Untie the string and peel away the leaves (don’t eat them) to reveal the sticky rice and tender pork. Serve with pickled chilli or radish and a sweet and salty soy-based dipping sauce. We’ve cut our bah-tzang open so that you can see the cross-section inside, but you would normally serve them unwrapped.