Ingredients

RICE CRÊPES AND FILLING

1. 1/2 cup rice flour
2. 1/2 cup cornstarch
3. 1/4 cup tapioca flour (see Note)
4. 1/2 teaspoon salt
5. 3 cups water
6. 2 tablespoons plus 2 teaspoons vegetable oil, plus more for brushing
7. 2 tablespoons dried tree ear mushroom pieces
8. 3/4 pound ground pork
9. 1 small onion, finely chopped
10. 1 tablespoon Asian fish sauce
11. Salt and freshly ground pepper
12. Nuoc Cham Sauce

GARNISHES

1. 1 large cucumber, peeled and thinly sliced
2. 1/2 cup fried shallots (see Note)
3. 1/2 cup mung bean sprouts

Directions

1. MAKE THE RICE CRÊPES AND FILLING: In a large bowl, whisk the rice flour with the cornstarch, tapioca flour and salt. Whisk in the water and 2 teaspoons of the oil until blended.
2. In a small bowl, cover the tree ear mushrooms with warm water and let stand until softened, about 5 minutes. Drain and chop the mushrooms.
3. In a small skillet, heat the remaining 2 tablespoons of oil. Add the ground pork and the onion and cook over moderate heat, breaking up the meat with a spatula, until no pink remains, about 4 minutes. Stir in the chopped mushrooms and the fish sauce and season with salt and pepper.
4. Preheat the oven to 425°. Oil 3 large baking sheets. Heat an 8-inch nonstick skillet and brush with oil. Whisk the rice-flour batter well. When the oil is hot, pour 2 tablespoons of the batter into the skillet, tilting and shaking the pan to evenly coat the bottom with batter. Cover and cook over moderate heat until the crêpe is firm, about 2 minutes. With a spatula, flip the crêpe and cook for 30 seconds longer. Flip the crêpe out flat onto a prepared baking sheet. Repeat with the remaining batter to make a total of 18 crêpes; don't let the crêpes overlap on the baking sheets or they will stick together.
5. Spoon about 2 tablespoons of the mushroom filling into the center of each crêpe and fold in the sides to cover the filling and form a neat square. Cover the crêpes with foil and bake until heated through, about 5 minutes.
6. Arrange the rice crêpe packets on a platter and spoon the Nuoc Cham Sauce over them. Scatter the cucumber slices, fried shallots and bean sprouts all over the crêpes and serve.

Make Ahead

The mushroom filling can be refrigerated overnight. The crêpe dumplings can stand at room temperature, covered, for up to 2 hours before baking.

Notes

Tapioca flour is available at specialty food stores. Fried shallots are available at Asian markets.