M&S Collection Spanish Pan Cristal Otherwise known as glass bread, due to its delicate, brittle crust, pan de cristal is a traditional topped bread from the Catalan region of Spain. This pan cristal is topped with mozzarella cheese, smoke cheese and Serrano ham. It's perfect for sharing as part of a tapas feast. Oven cooks in 14 minutes. Serves 2. Welcome to Collection from M&S, where exceptional quality and intricate attention to detail makes for something truly special.