Coffee cake with cinnamon crumb topping is such a classic breakfast. You won't believe how easy it is to make with boxed cake mix. A great way to feed a big family or house guests, makes 12 servings. Ready in 20 minutes.
Make batter. Using a hand mixer, in a large bowl, mix together cake mix, eggs, oil, cinnamon and water or milk. Beat until just blended.
Add batter to pan. Pour cake batter into a greased 9x12 pan.
Bake for 15 minutes.
Make crumble topping. While cake is baking, get a new bowl or clean the batter bowl, and mix together flour, sugar, brown sugar, cinnamon and cubed butter using an electric mixer. Beat on a high speed for about 2 minutes, or until big crumbles form.
Add crumbles to cake. After 15 minutes of baking, pull cake out of the oven and add crumble topping. Bake for an additional 3-5 minutes or until crumbles stick to the cake. Remove from oven and let cool.
Make icing. Prepare icing by beating powdered sugar, vanilla extract and milk together in a bowl.
Drizzle icing over cooled cake before serving.
Cut and serve. Slice cake into 12 squares and serve warm or make ahead the night before and seal with plastic wrap once cooled until morning.
Notes
For a boost of protein: substitute 1 egg for ¼ cup of vanilla or plain Greek yogurt.
For added moisture: get a cake mix with pudding in the mix of that's labeled "Super Moist"
When making icing: add milk slowly until you get to you desired thickness or icing. You don't need much.
Bake time can vary with the size, shape and material of your pan. Use a toothpick to test the center of the cake and bake longer if it does not come out clean.