In Germany, cakes called stollen are made at which time of year?

Stollen is a fruit bread of nuts, spices, and dried or candied fruit, coated with powdered sugar or icing sugar and often containing marzipan. It is a traditional German bread eaten during the Christmas season, when it is called Weihnachtsstollen (after "Weihnachten", the German word for Christmas) or Christstollen (after Christ).

The Advent season was a time of fasting, and bakers were not allowed to use butter, only oil, and the cake was tasteless and hard. In the 15th century, in medieval Saxony (in central Germany, north of Bavaria and south of Brandenburg), the Prince Elector Ernst (1441–1486) and his brother Duke Albrecht (1443–1500) decided to remedy this by writing to the Pope in Rome. The Saxon bakers needed to use butter, as oil in Saxony was expensive, hard to come by, and had to be made from turnips.

Pope Nicholas V (1397–1455), in 1450 denied the first appeal. Five popes died before finally, in 1490, Pope Innocent VIII (1432–1492) sent a letter, known as the "Butter-Letter", to the Prince. This granted the use of butter (without having to pay a fine), but only for the Prince-Elector and his family and household.