I am horrific at cooking but so desperate to be able to bake. Over the years I've followed various recipes and it's still hit or miss as to whether it's edible! Someone recently gave me the tip of weighing my eggs and matching the weight with flour, sugar and butter which worked perfectly (on more than one occasion!) I want to move on now. If I want to add banana for example can I just add banana or do I need to change the amount of the original ingredients?