Coffee cakes come with a variety of fillings and toppings. One popular variation is the crumb coffee cake, which is topped with chunks, or "crumbs," of sugar and spices. This type of coffee cake is most popular in the United States. Some German coffee cakes also have a similar crumb topping, but the German version typically is not referred to as crumb coffee cake.
In spite of the name, coffee cakes do not often contain coffee as an ingredient. Instead, they are popularly consumed along with a hot cup of coffee. A slice of homemade coffee cake is often eaten warm and freshly baked. Its popularity has made it a favorite among many small bakeries and even large, pre-packaged baked goods companies. When bought from a bakery or store, coffee cake is often reheated or simply eaten at room temperature.
A basic coffee cake is made from flour, sugar, baking powder, butter, eggs and milk. Many bakers add vanilla extract or various spices for additional flavor. The addition of sour cream also is popular and creates a cake that has more moisture.
Some coffee cakes have a glaze or drizzle of icing, but a crumb coffee cake has a dry-yet-sweet topping instead. The most basic crumb topping is made with flour, sugar and butter. Many bakers include cinnamon or other spices to further enhance the flavor. The addition of nuts, such as walnuts or almonds, is also common and gives the topping a crunchier texture with more dimension. Healthier, lower-fat versions of the cake frequently use oats in the crumb topping.
Many variations of crumb coffee cake have a moist layer of fruit filling that helps counter the dry nature of the crumb topping. The fruit filling also provides noticeable sweetness to an otherwise mild cake. Berry fillings, such as blueberry and raspberry, are especially common. Apple fillings are equally common and often appear in recipes that include cinnamon in the crumb topping.
Although coffee cake is popular all around the world, few variations of crumb coffee cake exist outside of the United States. Germany, however, has streusel kuchen, which traditionally is topped with a similar crumb mixture. This crumb mixture also includes sugar, flour and some type of fat. The fat might be in the form of butter, but lard or shortening occasionally is used instead. Unlike the American version of coffee cake, streusel kuchen usually contains yeast.