Melting crumb topping is a definite problem for coffee cakes. If the topping melts, it ruins the texture and flavor of the cake. A crumb topping typically consists of butter, sugar and flour. The crumbs are sprinkled over the coffee cake batter, and the cake is baked, to create a crunchy topping. Melted toppings soak into the cake as it bakes, leaving soggy results.
Crumb Topping 101
The most common cause for a melted crumb topping is too much butter. Cold or melted, it doesn’t take much butter to turn the flour and sugar into crumbs. Use around 5 tablespoons of butter for every 1 cup combined dry ingredients, such as flour and sugar, to create crunchy crumbs. Mix the butter into the dry ingredients thoroughly, until the entire mixture is made up of small clumps, to ensure good results. Leaving large clumps in the mix can result in soggy sections of the cake.