Cover the dried mushrooms in warmwater for 20 minutes, drain, dry and thinly slice.
Combine the rice flour, tapioca flour and salt with the water and whisk until the flours are dissolved and the mixture is smooth.
Heat a nonstick pan over medium heat, add 2 tablespoons of vegetable oil and saute the garlic and shallots until fragrant.
Add the pork, mushrooms, fish sauce, sugar and a pinch of salt and pepper.
Stir-fry for 4 minutes, then transfer to a bowl and set aside.
Heat a large non-stick frying pan over medium heat and add oil to coat base of pan.
Pour a small ladle of batter into the pan and swirl to cover the base, creating a thin layer.
Cover the pan with a lid and cook for 30 seconds.
Remove the lid, slide the mixture onto an oiled cutting board or tray, and place the pork/mushroom mixture atop the batter on one side.
Fold the cooked batter over to form a roll, and using a good pair of kitchen shears, cut the roll into 1-inch cross sections.
Remove the roll to a plate and top with the fresh mint, bean sprouts, fried shallots and a light drizzle of extra-virgin olive oil.
Repeat to make three more servings. Serve with a side of nuoc cham.