Use different proportions -- and ingredients -- to inspire your own creations.
Halve the roll. Drizzle cut sides with olive oil. Sprinkle with coarse salt and freshly ground pepper.
Layer mozzarella, Parmesan cheese, prosciutto di Parma, and basil leaves on bottom half. Top with other half.
Heat a grill pan over medium-low to medium heat until almost smoking. Lightly brush pan with olive oil. Place panino on pan; cover with a cast-iron or other heavy skillet weighed with soup cans. Gently press straight down. Grill, undisturbed, until browned and crisp on bottom, 3 to 4 minutes. With a spatula, flip panino. Repeat process, grill until crisp and browned on other side, 3 to 4 minutes more. Serve hot.