Heat oven to 350°F. Spray cookie sheet with cooking spray.
Place biscuits on microwavable plate. Microwave uncovered on Medium (50%) 30 to 45 seconds, turning over halfway through microwave time. (Biscuits should still be cold for easier handling.) Press and stretch each biscuit into 6-inch round.
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.
Bake 15 to 20 minutes or until golden brown.