Heat the oil in a large skillet over medium-high heat.
Cook the onion, garlic, and ginger until just soft and aromatic, about 3 minutes.
Add the pork and cook until no longer pink, about 5 minutes. Drain excess fat, if desired.
Add the coleslaw mix (or cabbage and carrots), bean sprouts (if using), scallions, hoisin sauce, soy sauce, and sesame oil. Mix together with a large spoon.
Working one roll at a time, place about 2 tablespoons of the filling across the center of a wrapper. Brush all four sides of the wrapper with a little water. Fold the bottom corner over the filling and gently tuck in. Next, fold the two sides in and tuck the sides in. Brush a little more water over the top. Roll the egg roll to enclose and the flap is sealed. (See image in post for reference).
Heat enough of the vegetable oil in a large skillet to cover a roll, about 2 to 3 inches. Heat the oil to 350°F (using a candy thermometer ensures correct temperature).
Using a fork, gently slide 1 or 2 of the rolls into the hot oil. Using a couple of forks, keep the rolls submerged until browned all over, flipping a couple of times. About 2 minutes. Repeat with remaining rolls.
To make the duck sauce, mix together all ingredients in a small bowl. Refrigerate until ready to use.