Chocolate-Orange Cake

At Vienna’s esteemed Demel, those who want a sweet that isn’t too sweet might choose a slice of Burgtheatertorte. Bakers never let anything go to waste, even cake crumbs, and they are used here to make a moist chocolate-almond cake dotted with candied orange peel. The 4 cups of cake crumbs are easily obtained during a day’s work at a bakery, where the tops of countless cakes are routinely trimmed off, but home cooks will need a strategy (unless you are a frequent baker and freeze tri