In a bowl, mix together rice flour, salt, oil, and water until you get a smooth paste-like consistency.
Place banana leaves on your work surface and spread some of the paste in the center.
Place the wood ear mushroom, pork, shrimp, minced garlic, shallot, and green onion in the center of the paste. Add a teaspoon of oyster sauce to enhance the flavor.
Fold each side of the banana leaves over the filling until it is completely enclosed.
Place your Banh nam in a steamer and steam for about 30 minutes or until it is cooked through. Serve your Banh nam with some dipping sauces.