Slice the sub rolls if needed. Add the mayo to both sides. Add the mustard to the mayo. Set aside
Add EVOO to a hot skillet, prefer cast iron. Add onion. Saute until onion starts to turn clear. Add the chipped bologna. toss till bologna starts to brown. don't let it get too dark/burnt. remove from heat and add cheese over bologna.
transfer bologna/onion/cheese to roll. top with crushed chips. serve