Place ham bone in a 6-qt. electric pressure cooker. Add water, beer, peas, celery, carrot, onion and mustard. Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 15 minutes. Let pressure release naturally. , Remove ham bone from soup. Cool slightly, trim away fat and remove meat from bone; discard fat and bone. Cut meat into bite-sized pieces; return to pressure cooker. Stir in remaining ingredients. If desired, top with additional minced parsley.