A kammerjunker is a type of dry, crunchy cookie — or "biscuit," in British English — from Denmark. Kammerjunker is sometimes translated "rusk" in English, even though this translation may not be any more familiar than the original Danish. It is traditionally eaten with a cold dessert soup.
On its own, the kammerjunker is not a particularly flavorful cookie, being composed simply of milk, eggs, butter and a bit of sugar. It may sometimes be accented with lemon zest or cardamom for added flavor, but more commonly it is not eaten alone. The traditional way to eat kammerjunkers is to crush them up in a bowl of koldskål,which is a yogurt-based or buttermilk-based dessert soup that translates simply, "cold bowl."
Koldskål is made with lemon, which causes the yogurt or buttermilk base to sour or curdle. It may contain a number of other ingredients, such as beaten egg whites or vanilla extract. It is nearly always served with kammerjunkers, but may sometimes be mixed with brown sugar and drunk by the glass. The cookie-and-soup combination may sometimes be sold together in Danish restaurants under the moniker koldskål med kammerjunker. Since it is served cold, this dish is eaten almost exclusively in the summertime.
Someone living outside Denmark and wishing to approximate koldskål with kammerjunker has a few options. Going the homemade route, he or she might find an authentic kammerjunker recipe or approximate one with a recipe for another crunchy butter cookie. Alternatively, this person could use store-bought cookies. The nearest equivalent to kammerjunkers sold in an average American grocery stores is generally agreed to be vanilla wafers. There is no commonly available equivalent to koldskål in the US, so it must be prepared from scratch. Fortunately, however, it is quick and easy to make as the ingredients are simply mixed into the base and chilled for an hour before serving.