pearl sugar
Hard, opaque white sugar nuggets that hold their shape in the oven and stay on top of baked goods as a crunchy topping.
Pearl sugar is sugar compressed into firm, matte white grains that do not melt in the oven. In German-speaking countries it sits in the baking aisle of almost every supermarket; in English-speaking countries it is more often found in Scandinavian shops, delicatessens or online.
Substitute:
Roughly crushed sugar cubes come closest, though the pieces are more irregular and soften slightly at the edges. Belgian pearl sugar, made for Liège waffles, is much larger and does not work as a topping.