Create an assembly line by placing a stack of breaded cutlets next to a stack of sliced salami (if using), and the bowl of filling. Place a few cutlets down on a cutting board, then lay a piece or two of salami (if using) on top. Place a heaping teaspoon of filling on top of the salami, being careful not to put too much. At this point, you can choose to roll them up like cigars or bunch the meat up into a pouch and use two toothpicks to hold it closed.
Place the spiedini into a greased baking dish. Be sure to pack them in tight, as this will help them cook evenly. Preheat the oven to 425 degrees.
Once all the spiedini are made, spoon any extra sauce, onion, or breadcrumb mixture into any holes in the pan. Use it all up to help keep the spiedini moist, and not to waste any. If you don’t have any mixture left, you can mix together a little sauce and breadcrumbs. No need to chop more onions and cheese for this part if you don’t have any left.
Break up some pieces of dried bay leaves and tuck them in between each spiedini. This is optional, but gives them a nice, subtle flavor.
Cover the pan with foil and bake for 15 minutes. Remove the foil and bake for another 10 minutes or so until the breadcrumbs are golden brown. Serve hot or warm.