In a bowl, combine ground pork, scallions, garlic powder, salt, pepper, oyster sauce, egg, and cornstarch. Mix until thoroughly combined.
Peel and devein the shrimp, keeping the tail intact. To prevent them from curling during cooking, make shallow cuts on the underside of each shrimp, making sure not to slice all the way through.
Cut the wrappers diagonally in half to create two triangles. Place one triangle on a clean surface with the pointed corner facing one direction and the straight edge on the opposite side.
Position the shrimp in the center, with its tail extending out. Spoon a tablespoon of the meat mixture over the shrimp, forming it into a log shape along the length of the shrimp.
Fold the opposite side of the wrapper over the filling, then wrap the bottom of the wrapper snugly over it. Gently fold in the area near the shrimp tail to secure it, making sure the tail peeks out neatly.
Roll the lumpia tightly, sealing the edges with water or egg wash, depending on the wrapper type. The egg wash can provide extra hold, especially for certain wrappers that might not stick well with water alone.
As you finish rolling the lumpia, carefully fold in the area where the shrimp tail sticks out to ensure the lumpia is well-sealed and the filling is enclosed.Double wrap the lumpia if the wrappers are thin, to ensure they hold their shape and contain the filling securely during cooking. In a saucepan or deep pan, heat about an inch of oil over medium-high heat. Fry the spring rolls in batches for about 8 minutes, until they turn golden brown and crispy. Turn them occasionally for even cooking.PRO TIP: For lumpia that stays crispy, begin by frying them at a high temperature. Once they sizzle, slightly reduce the heat so the lumpia becomes thoroughly crispy without browning too quickly. Remove the fried lumpia from the oil and drain on a wire rack or on paper towels to remove excess oil.
Serve and enjoy your Shrimp Lumpia hot with your favorite dipping sauce.