Chef's tips: Eska's sourdough koláč are topped with fresh seasonal fruit, as well as preserved or frozen fruit (strawberries, blackberries, raspberries, apricots, plums, or pears in caramel). Other traditional fillings include poppyseed, custard, pudding, or nuts. Moravian koláč is filled with fruit curd or thick pudding. Lard is added to the dough for flavor and suppleness. Leaving the pastries to rest in a cool place gives the yeast time to work and creates a softer and better-rising dough that's ready to bake in the morning.