In small bowl, stir mustard and mayonnaise until smooth. Spread mustard mixture on each round to within 1/2 inch of edge. Arrange pork and ham slices over mustard mixture to within 1/2 inch of edge, folding if necessary. Top each round with two pickle slices; sprinkle with cheese. Brush egg around edge of biscuit rounds. Fold dough over filling; press edges with fork to seal. Brush with egg; sprinkle with onion.