Schwarzer magister is a traditional dessert that's especially popular in the region of Rhineland-Palatinate. It's usually made with a combination of zwieback rusks (or toasted white bread), prunes, eggs, lemon juice and zest, sugar, cinnamon, heavy cream, and salt.
The prunes, lemon peel, sugar, and cinnamon sticks are boiled in water, and the liquid is poured into a baking dish. It's topped with zwieback, prunes, and another layer of zwieback. The process is repeated until all the prunes and zwieback are used.
The egg yolks are beaten with sugar, cinnamon, lemon juice and zest, and prune liquid until creamy. The egg whites are beaten with salt, the heavy cream is whisked into peaks, and both are folded into the batter that's spread over the final layer of zwieback.