Wash the dong leaves and let them dry. Soften the banana leaves by passing them over a flame, then wash and dry them.

Cut the pork into thin strips about 1/5 inch (5mm) thick. Season and stir-fry until cooked. Use plenty of shallots; fry them until fragrant. Slice the wood ear mushrooms into thin strips and stir-fry as well.

Mix the pork, wood ear mushrooms, fried shallots, and scallions together, then stir-fry again. Adjust seasoning to taste—this is your filling.

Soak the dry rice flour in 5 1/4 cups water (about 1.25 liters) for 3 to 5 hours until the batter is elastic (if using fresh, clean flour). If using wet flour, test by dropping a bit on the back of your hand: if it runs a bit and then leaves a white mark, it's ready; if it dries immediately and doesn't run, add more water. Add about 1 teaspoon salt. Cook the batter on the stove, stirring constantly with a large chopstick or spoon, until it thickens to a paste (it doesn't need to be fully cooked). This is the most important step for making bánh tẻ.

To assemble: Work quickly while the batter is still hot for the best texture. Lay out a dong leaf, spread a thin layer of batter on it. Add a line of filling down the center.

Fold the edges of the leaf over the batter, rolling it tightly so the cake is round and compact, with no excess batter leaking out. Place this roll on a banana leaf, roll it up, fold both ends, and tie securely with string.

Steam the cakes for about 20 minutes. Some people prefer to eat them hot, while others like them cooled.

Serve with fish sauce or chili sauce for dipping.