Hi Kat, was the frosting at room temperature when you added the crumbled cake? If it’s too cold, the mixture will be a bit crumbly as you mention. And how did you measure your flour for the cake? Be sure to spoon and level (or use a kitchen scale) to ensure the flour isn’t over-measured, which can dry out the cake. Over baking can dry it out, too. Hope this helps for your next batch!

Hi Susan, you’ll use the same about. 16 ounces but with 1/2 teaspoon vegetable oil.