The mild taste of the Swiss cheese, the creamy texture of the Provolone cheese and the saltiness of the Feta cheese make for a winning combination in this three cheese panini.
Spread mayo on two slices of sourdough bread. On the first one, add Swiss cheese slices. Add a mix of Feta cheese crumbles, spinach and pesto. Add Provolone cheese slices, avocado slices and top with the second piece of bread before grilling.