Finely chop green olives, black olives and giardiniera and pepperoncino; place mixture in a medium mixing bowl.
Add remaining ingredients (garlic, parsley, basil, salt, pepper, red wine vinegar and olive oil); stir until well combined. Cover and refrigerate overnight.
For the Paninis
Brush a large frying or grill pan with olive oil; place the bottom half of each ciabatta roll in the pan. Place pan over medium heat.
Meanwhile, spread 2-3 Tbsp (or more!) of olive spread mixture onto the other half of the ciabatta rolls; set aside.
Divide meats (soppressata, salami and mortadella) and cheese evenly onto rolls in grill pan. Top with other half and cook over medium heat for 4-5 minutes per side, or until cheese is fully melted.
Notes
The Olive Spread recipe makes more than you need for these sandwiches. Feel free to cut it back…or just use it as a dip with pita chips!