Combine pork, 1 teaspoon soy sauce, sherry and garlic; mix well. Let stand 15 minutes.
In a large skillet, brown meat in 2 tablespoons oil. Add bean sprouts, onion, and 1 tablespoon soy sauce. Cook, stirring constantly, until vegetables are tender, but still crisp. Drain and cool.
Dissolve cornstarch in 1/4 cup water. Place about 1/3 cup vegetable-meat mixture on the lower half of an egg roll skin. Moisten left and right edges with cornstarch mixture. Fold bottom edge up just enough to cover fillings, left and right edges 1/2-inch over, and roll as for jelly roll. Moisten top edge with cornstarch mixture and seal. Continue with the rest of the spring rolls.
Mix together bisquick, 1/2 cup water and egg. Dip each roll in batter. Deep fry in oil until golden brown. Drain.
Slice each roll into 4 pieces. Serve with hot mustard, catsup or sweet and sour sauce if desired. Makes 8 spring rolls.