Heat panini grill.
Slice ciabatta bread in half. Over a preheated hot grill or under broiler, using tongs, grill bread until grill marks appear about 2 to 4 minutes. Using a rubber spatula spread 4 tablespoons of white truffle butter on bread. Layer lettuce, sopressata, mozzarella, prosciutto, radicchio, sun-dried peppers, and basil leaves. Drizzle olive oil and balsamic vinegar and add salt and pepper, to taste. Cover sandwich with top piece of bread and cut into 4 equal pieces. Place sandwich on panini press until bread is toasted and cheese is melted about 5 minutes. Remove from grill and serve.