This is quite possibly one of the most common baking problems I hear about, which is such a shame because it’s very easily prevented. It’s an issue of simply not baking the item in question for long enough, even though it may look browned to perfection on the outside. Always be sure to check the interior by inserting a toothpick or wooden skewer into the center, all the way down to the bottom. This method does have its pitfalls though, should there be chocolate chips that give the false impression that your cake is still raw in the middle, so you may wish to poke in multiple places. Bear in mind that the holes will show, so unless you’re covering the top with frosting, this may not be the best idea!