In a large pot, combine the white vinegar, water, red pepper flakes, salt, sugar
, and garlic and bring to a boil over medium heat. Once boiling, remove the pot from the heat and add the sliced peppers and onions
. Let the ingredients pickle
at room temperature for about 30 minutes. The peppers will last up to 1 month in a re-sealable container that has been stored in fridge.
Preheat an outdoor grill or grill pan
over medium-high heat. Arrange the butterflied sausages
on the grill, cut side down. Cover the sausages with a sheet pan
and weigh it down with a tea
kettle filled with water or a heavy pan. Grill for 4 to 5 minutes per side.
Slice the rolls in half and brush them, inside and out, with the olive oil
. Layer a slice of provolone
over the bottom half of each roll. Add the cooked sausages to the cheese
, top with some of the pickled peppers and onions, then finish with 3 pieces of shaved Parmesan
and, finally, cover with the top half of each roll. Put the sandwiches in a panini
press, 2 or 3 at a time, and cook until the bread is crisp
and cheese is melted, about 4 to 5 minutes. If you do not have a panini press, grill the sandwiches in a large skillet over medium heat and put a cast iron or heavy-bottomed pan on the sandwiches to flatten. Cook for 3 minutes per side. Transfer the sandwiches to a serving platter and serve.