Many central European recipes call for bread or cake crumbs as a batter ingredient or as a garnish. The use of crumbs in a batter goes back to when cooks were especially frugal and needed ways to use up stale baked goods. Both types of fresh crumbs can be made in a food processor or blender. Dried unflavored bread crumbs are easily purchased.
Fresh bread crumbs should be made from sturdy white bread with a tender crust. White sandwich bread or soft-crusted French bread are perfect. If you don’t want to buy a whole loaf, use a dinner roll or two. I never trim the crust when making bread crumbs. Get in the habit of turning day-old bread into bread crumbs and storing them in a self-sealing plastic bag in the freezer for up to three months.
Dried bread crumbs, so easy to purchase at the supermarket, aren’t worth the trouble to make from scratch. I used to balk at recipes that asked to coat the pans with bread crumbs because I didn’t always have them in the cupboard. But the bakers I worked with in central Europe convinced me that a coating of butter and bread crumbs is the best coating for fluted tube pans like Gugelhupf molds. If you are concerned about using up the entire box before it goes rancid (although the crumbs seem to last forever when airtight), store it in the freezer. Of course, be sure you buy the unseasoned variety.
In bakeries, there is a constant supply of cake crumbs created from trimmings. In a home kitchen, this isn’t the case, although you could save up a stash of trimmings in the freezer (not likely). If you need a small amount (less than ½ cup) of crumbs as a garnish, these can usually be culled by trimming off a very thin layer from the top of the cake. Or, purchase an inexpensive pound cake or even a muffin. If you do a lot of this kind of baking, you may want to store a pound cake in the freezer just for the purpose of having cake crumbs handy. When needed, slice off a piece; it will defrost quickly. For the Burgtheatertorte, you will probably have to bake a separate chocolate cake to acquire the necessary 4 cups of crumbs, but it is worth the effort.