You don't just "make" this sandwich, you "build" it with love! The fresh mozzarella in place of traditional provolone cheese (which is often used in subs) adds instant elegance and freshness. Topping the cured meats and creamy cheese with a tangy vinaigrette helps balance the richness of the sandwich.
Technique tip: Using paper-thin cuts of meat really enhances the flavor.
Swap option: You can use chili powder instead of Calabrian chili.
In a bowl, combine olive oil, red wine vinegar, 2 teaspoons of the oregano, salt, pepper and garlic. Whisk and let sit in the bowl. Set aside.2.
In a separate bowl, place red onion and add cold water to cover; let soak 10 minutes. Drain and use paper to pat very dry. Set aside.3.
Stir Calabrian chili paste and mayonnaise together until fully incorporated.4.
Discard garlic from the vinaigrette and whisk again.5.
Spread chili mayo over the top part of the roll. Spoon a teaspoon or two of vinaigrette on the bottom of the roll and add shredded romaine on top.6.
Drape a single layer of meat slices so that they fold over themselves over the length of the bottom of the roll. Then, add a single layer of the mozzarella cheese on top of the meat. Alternate red onion slices with slices of pepperoncini. Repeat the process until the sub roll is full.7.
Drizzle vinaigrette on top. Garnish with a final sprinkle of dried oregano. Close sandwich and cut in half crosswise, to serve.