Prepare the filling: Dice pork belly into small cubes and devein shrimp, leaving them whole or cutting in half depending on size. In a bowl, combine pork and shrimp with minced garlic, fish sauce, black pepper, and a pinch of sugar. Mix well and marinate for 20 minutes.

Make the dough: In a large mixing bowl, combine tapioca starch with salt. Bring water to a rolling boil and gradually pour into the starch while stirring vigorously with a wooden spoon. The mixture will become translucent and sticky. Once cool enough to handle, knead for 3-4 minutes until smooth and pliable. Cover with a damp cloth.

Prepare banana leaves: If using fresh banana leaves, briefly pass them over an open flame or dip in boiling water to make them pliable. Cut into 4-inch squares. Lightly brush each square with vegetable oil.

Assemble dumplings: Take a small portion of dough (about 1 tablespoon) and flatten it in your palm into a thin circle. Place 1 shrimp and a few pieces of pork in the center. Carefully fold the dough over the filling, pinching edges to seal completely. The wrapper should be translucent enough to see the filling.

Wrap in banana leaves: Place each dumpling on an oiled banana leaf square and fold the leaf around it, securing the ends underneath.

Steam the dumplings: Arrange wrapped dumplings in a steamer basket, making sure they do not touch. Steam over high heat for 20-25 minutes until the wrappers become completely translucent and glossy.

Prepare dipping sauce: Combine fish sauce, lime juice, water, sugar, minced garlic, and sliced chili peppers. Stir until sugar dissolves. Adjust seasoning to taste.

Serve immediately: Unwrap the banana leaves at the table and serve hot dumplings with the dipping sauce and fresh herbs on the side.