In a small bowl, combine dung mein fun, tapioca flour and salt; set aside. Place water into a small pot and bring to a boil and add oil. Remove pot from the heat and stir in dry ingredients with a wooden spoon until all white powder lumps are incorporated. Cover mixture and let sit for 15 minutes until cool. Remove the dough from the pot. With oiled hands, knead for 15 minutes. Pinch off 1 1/2-inch sized clumps of dough and squeeze into balls (about 15 balls).
Brush working surface and rolling pin with oil and roll each ball into a thin circle about 3-31/2inches in diameter. Place about 1 tablespoon of filling into the center and bring the edges together to form a half moon-crescent shape. Pinch and crimp the edges to seal.
Grease the steamer rack with vegetable or peanut oil and overlap gok jai in one layer on the rack. Lightly brush gok jai with oil and steam for 20 minutes. Cool and serve. Makes 15 servings.
Approximate Nutrient Analysis per serving:
150 calories, 10 g fat, 3 g saturated fat, 35 mg cholesterol, 250 mg sodium, 11 g carbohydrate, 0 g fiber, 0 g sugar, 6 g protein