In a bowl, combine pork, shrimp, water-chestnuts, mushrooms, Scallions and carrots. Season with salt, pepper then mix in egg and soy sauce. Beat mixture thoroughly.
At one end of a lumpia wrapper, spoon about 2 tb of the pork mixture and roll tightly. Brush end of wrapper with water to seal.
Heat the oil in a deep-fryer or heavy skillet to 375 degrees F (190 degrees C). Fry 3 or 4 lumpia at a time. Fry for about 3 or 4 minutes, turning once. Lumpia are cooked through when they float, and the wrapper is golden brown. Cut in half, or serve as is with sweet and spicy dipping sauce.
Most home cooks pack too much filling into each wrapper, which traps internal moisture and prevents the exterior from achieving crispness before the meat burns. Achieving the ideal texture relies on mechanical protein extraction. Thoroughly beating the ground pork and finely chopped shrimp cross-links the myosin filaments into a cohesive matrix that holds the water chestnuts, mushrooms, carrots, and scallions without releasing excess liquid during cooking. Rehydrating dried mushrooms in warm chicken broth infuses umami-rich glutamate compounds directly into the fungal tissue, supplementing the natural ribonucleotides found in the pork and shrimp. Managing the thermal mass of the frying medium requires a deep-fryer or heavy skillet maintained strictly at 375 degrees Fahrenheit. Crowding the vessel drops the oil temperature rapidly, leading to soggy, oil-saturated wrappers instead of a rigid, golden-brown crust. Processing only three or four rolls at a time ensures the oil recovers its heat instantly. Floating serves as the primary visual indicator of doneness, signaling that internal water has converted to steam and the surrounding proteins are fully set. This stage typically requires three to four minutes of total immersion, with a single rotation halfway through to guarantee even heat transfer across the cylindrical geometry.