Make the batter: Combine 2 cups rice flour and 1 cup tapioca starch in a bowl. Add salt and sugar, then slowly mix in the coconut milk. Add 4 1/4 cups water (about 1,000 ml) and stir until smooth. Add 1 tablespoon vegetable oil and let the batter rest.

For the filling: Soak the dried shiitake mushrooms until soft. Peel and dice the jicama, carrot, onion, shrimp, and pork into small cubes. Chop the green onions and microwave them with oil for 30 seconds. Keep each ingredient separate, then season lightly for flavor. First, sauté the shallot, then add the jicama and stir-fry. Next, add the carrot and mushrooms, stir until the jicama softens, then remove from the pan.

Continue by stir-frying the pork and shrimp. When they are cooked through, return the jicama mixture to the pan and mix well. Season to taste, then add the diced onion. Turn off the heat and add 1 tablespoon black pepper.

Steam the batter: Pour the batter into a pan and stir constantly over medium heat until it thickens to a paste. Grease two molds with oil and divide the batter evenly between them.

Place the molds in a steamer, cover to prevent water from dripping onto the batter, and steam for about 40 minutes over medium heat.

Let the bánh đúc cool before removing and cutting into pieces. Top with the shrimp and pork filling, green onion oil, and fried shallots. Serve with dipping fish sauce and pickled vegetables.