Using a meat grinder, grind the shrimp and pork together and set aside. Soak the mushrooms and tree ear in hot water for ten minutes then chop finely.
Cooking the meat mixture: Heat a wok or large frying pan over high heat until very hot. Add the pork and cook for about two minutes until it is no longer pink. Add the shrimp and cook for another two minutes until it is pink. Add the scallions, soy sauce and black pepper. Cook until the liquid has evaporated. Strain the excess fat off the meat and then spread on a large plate or cookie sheet to cool.
Cooking the vegetables: With the same wok, heat the two tablespoons of canola oil over high heat. Add the ginger, water chestnuts, bamoo shoots and mushrooms and cook for two minutes. Add the celery and carrots and cook for another minute. Add the cabbage and bean sprouts and cook until the cabbage starts to wilt. Remove from heat and strain any excess liquid off the vegetable mixture and spread over the meat mixture. Drizzle sesame oil over the mixture. Cool.
Prepare your work area: Once the mixture has cooled down, mix the two mixtures together. Beat an egg and place in a bowl on a large work surface next to the egg roll wrappers. Place a sheet of waxed paper on a cookie sheet and dust with corn starch.
To fill the egg rolls: Take one wrapper and place it in front of you forming a diamond shape. Brush the top two edges of the wrapper with egg. Spread a small handful of the filling just below the middle of the wrapper. Pull the bottom of the wrapper up over the filling and tuck it around the filling. brush the two ends of the wrapper on either side of the filling with more egg. Bring each side up over the top the filled portion. Roll up, tucking the wrapper up to form a tight roll.
Cooking the rolls: If you are going to fry the rolls, heat a few inches of oil in a heavy pot or dutch oven to 375 degrees. Drop about 4-6 rolls at a time in the oil and cook till golden brown on both sides. If steaming the rolls, steam in a steamer lined with lettuce leaves to prevent steaming for about 5 minutes.