Mix together the mayonnaise, minced garlic, parmesan cheese, fresh parsley, red wine vinegar, spicy mustard, oregano and red pepper flakes until well combined. Season with salt and pepper to taste.
Toss together the mixed dressing with the shredded lettuce, sliced red onion and pepperoncini peppers in a large mixing bowl until well combined. Cover and refrigerate until ready to use.
Mix all butter ingredients in a small mixing bowl until well combined and set aside.
Slice your sub sandwich rolls in half lengthwise and place the tops and bottoms of the rolls onto a large baking sheet. Evenly brush the tops of the rolls with the prepared garlic butter mixture.
Add two slices of provolone cheese onto the bottoms of the rolls. Place the baking tray under your broiler for 1 to 3 minutes, or until the cheese has melted and the tops of the rolls are lightly golden and toasted.
To serve, divide the pastrami between your sandwiches on top of the melted cheese.
Divide the grinder salad filling evenly between each sandwich.
Place the tops on and serve as is or slice and serve. Enjoy!