Lay out one spring roll wrapper with the point facing toward you, so that it looks like a diamond. Lay a piece of sliced Serrano on top, then add a spoonful of the pork-cheese-and-pickle mixture, and sprinkle a little bit more cheese on top of that. Brush beaten egg over the edges of the wrap. Then fold the bottom point of the wrapper over the filling so that it extends 1/3 of the way up the length of the wrapper. Fold the right and left sides of the wrapper over that and roll it up tightly. Deep fry rolls until browned on the outside and gooey on the inside, about 2 minutes. Combine mustard and mayonnaise in a small bowl and serve as a dipping sauce.