Baked goods are particularly difficult for some people to get right, and one of the baker's problems is consistency--how to achieve that perfect balance between chewiness and cakeyness. (I know there's no such word, but there ought to be.)
It turns out that the difference between chewiness and cakeyness is all down to saturated vs. unsaturated fats and their proportion in each recipe. By varying the proportions (and carefully noting them down), it is possible to achieve the perfect consistency in your baked goods. Please remember that some saturated fats are not good for you: avoid Crisco and the like, and choose instead those saturated fats that are naturally saturated: coconut oil or butter.
If you use boxed cookie or brownie mixes, you know that you have to add oil. The reason for this is that the saturated fat component is already in the box (in the form of "milk solids" or something else). And what should you use for an oil? If you are not allergic to tree nuts, I recommend walnut oil, almond oil, hazelnut oil or another tree nut oil. These are not suitable for frying because of their low smoke points, but are perfect for baking or salad dressings. Nut oils add a subtle enhancement of flavour to your baked goods (called "flavour layering" that is all the rage with the popular chefs nowadays), and in addition, provide health benefits not available from the more popular corn, vegetable, or canola oils. I am all for variety in people's diets, and so I would recommend trying, at least in small quantities, some of these other oils for their varied nutritional benefits and flavours.