1. Spread the pesto evenly on all four slices of bread, slice the tomatoes, and place on two of the bread slices. Slice the mozzarella as well and place on top of the tomatoes. Add some fresh basil leaves and drizzle with some crema con Aceto Balsamico. Sprinkle with some grated Parmigiano (optional), season with salt and pepper, and then close the sandwiches with the two other bread slices. Spread the butter (or mayonnaise) on the outside of the sandwiches.

2. Heat up a panini grill or a griddle pan and grill the sandwiches from both sides until nicely browned and the cheese has melted. Cut in half and serve hot.