You make a coffee cake by mixing flour, sugar, butter, baking powder, and milk to create a rich batter, then layering it with a sweet cinnamon streusel crumb topping. Pour half of the batter into a greased baking pan, sprinkle part of the cinnamon sugar mixture inside, and add the remaining batter on top. Finish by scattering the rest of the buttery brown sugar crumbles over the surface before baking at three hundred and fifty degrees. This classic pastry pairs wonderfully with a warm morning cup of coffee.