Heat a skillet or frying pan on medium-high heat. Add a tiny bit of neutral oil.
Make three small piles of mortadella and cook until browned and crispy.
Flip the mortadella piles and add provolone cheese. Stack the piles on top of each other.
Slice the bun in half and toast each side in the remaining grease in the skillet.
Spread mayo on one bun half and mustard on the other.
Assemble the sandwich and enjoy.
