Heat oven to 400F. Separate dough into 10 biscuits. Using a rolling pin, roll each biscuit into a 5-inch round. In small bowl, combine ham, mustard and onion. Spoon about 2 tablespoons mixture onto center of each biscuit. Fold dough in half over filling. Press edges with fork to seal. Place on ungreased cookie sheet. Bake at 400F for 10 to 13 minutes or until golden brown.