Clean the mussels thoroughly and steam them until cooked. Once cooked, remove the mussels from their shells and set aside. Rinse the bean sprouts and let them drain. Wash and slice the green onions and cilantro, then set aside.

Prepare the batter by mixing the cornstarch with water and stirring until smooth. Add the tempura or all-purpose flour and mix well. Beat the eggs, then add the mussels. Season with sugar, fish sauce, oyster sauce, and soy sauce. Add the sliced green onions. Beat until frothy. When the oil is hot, pour the mixture into the pan and fry until crispy to your liking.

Heat a cast iron skillet until hot and add a little vegetable oil. Add the bean sprouts to the pan, then place the fried mussel pancake on top of the bean sprouts. Sprinkle with ground black pepper and garnish with green onions and cilantro. Serve hot.

For the dipping sauce, mix sweet chili sauce and chili sauce together for a quick and easy dip.