In a wok set over moderately high heat, add the ground ginger, onion, and celery and stir-fry for 1 minute. Add the cabbage and bean sprouts and stir fry 2-3 minutes more, or until vegetables are slightly softened. Add the pork and/or shrimp and stir-fry 1 minute more.
Add the chicken stock and sugar, bring the mixture to a boil and stir in the cornstarch mixture. Simmer until lightly thickened. Stir in sesame oil, salt and pepper to taste.
Have 1 cup water at a boil. Remove from heat and whisk in cornstarch mixture.
Have 12 egg roll wrappers ready under a dampened towel. Place a portion of the filing in a line diagonally across one corner of wrapper, brush with some of cornstarch paste and fold in the ends. Roll tightly to make a sealed cylinder. Repeat with remaining wrappers.
Heat oil to 350 degrees F. Fry egg rolls, in small batches, turning often, for about 4 minutes, or until golden brown. Transfer to paper towels to drain