Coffee cakes are typically sweet baked goods traditionally served with coffee or tea. While a regular cake can be called "coffee cake" if it is coffee flavored, the term usually refers to a cake designed to be eaten as a breakfast cake or served with coffee. There are many different flavors of coffee cake icing to choose from, though these cakes are not usually frosted in the traditional sense; most of the time they are finished off with a thin glaze, a sprinkling of powdered sugar, or some type of streusel topping.
Icing for coffee cakes usually refers to a sweet glaze. The glaze is traditionally made by mixing powdered sugar, milk and any special flavor ingredients. It is generally poured or drizzled over the top of the cake. Thicker frostings such as buttercream frosting or royal icing that hardens are generally not used as coffee cake frosting. People who prefer those types of frosting may use them, and they should still taste good, but it is not the traditional way coffee cakes are served.
Coffee cake icing need not be icing at all. Some cakes are so moist and flavorful that a sprinkling of powdered sugar is enough to top the cake. Very moist coffee cakes that are already incredibly sweet are often eaten without any type of coffee cake icing at all. Sometimes cake eaten without icing is referred to as snack cake, but coffee cake ingredients may still be used.
One of the most common types of coffee cake toppings is known as streusel. This is a crumb topping that usually contains ingredients such as flour, butter and sugar. Chopped nuts are sometimes added to make a nut streusel. Often, this is the only topping on a coffee cake instead of sprinkled sugar or glaze. Streusel-topped cakes are sometimes also referred to as crumb cakes, but crumb cakes usually have a much larger percentage of crumb topping than coffee cakes.
Baking coffee cake streusel generally requires no extra cooking time because the streusel is usually added when the cake goes into the oven. The ingredients should be blended together to form a crumb mixture that is sprinkled over the top of the batter. Coffee cake icing that is a glaze or thicker spread will almost never be baked; the icing is typically poured on after the cake is cooled to prevent it from thinning too much and running to the bottom.
Coffee cake icing is generally flavored to match the cake in some way. Cakes that contain fruit may be topped with a glaze that has a hint of their flavor, for instance, such as orange glaze for an orange and cranberry cake or cinnamon glaze for an apple-cinnamon cake. Vanilla glaze made from powdered sugar, water and vanilla extract is a standby that typically works well with any flavor. Streusel or sprinkled powdered sugar also tend to work well on almost any type of coffee cake.