Miss Jayne is correct - baking recipes assume a large egg - not small, medium, extra large or jumbo. Those sizes will all affect the outcome. Eggs are leaveners in baking and will make things fluffier and more cake-like. Really serious, professional bakers use weights as measurements (like XX grams eggs) as opposed to "one egg" or "juice of one lemon" (which can vary wildly), etc. Baking is like chemistry - an exact science - every little thing can affect the outcome. Cooking is more like art - a dash of this here, a pinch of that there, and you're good to go. Cooking is much more forgiving than baking... but the results of baking are worth the extra effort!
Other things to consider:
- how evenly does your oven bake? Are there hot and cold spots? If so, consider rotating pans halfway through or even more often to get a more even bake.
- is the temperature gauge on your oven accurate? If you oven isn't electric AND fairly new (under 10 years old), then it is worth your while to hop down to the store (
Walmart, Target, Bed Bath and Beyond, etc.) and get an inexpensive oven thermometer. Use that to read the temperature and never bake at anything but the exact recommended temperature for a recipe.
- following directions. Like I said, baking is a very exact science. Recipes come with detailed instructions for a reason - because following them precisely matters. I made a cake once and a lady liked it so much she asked me for the recipe. I wrote it all out for her in detail with lots of extra hints and instructions. When she made it she said it turned our terribly. I asked her if she followed the instructions and she said, "oh, no... I'm not one for instructions. I just kinda tossed it all in a bowl and stirred it up then baked it!" This is something you can't do with baking - if it says beat ROOM TEMPERATURE butter and sugars together until light, fluffy, and creamy - do exactly that. Don't melt the butter. Don't use hard, cold butter. Dont' just stir them together. BEAT them until light, fluffy, and creamy. Every detail matters in baking. Follow the instructions, make slight adjustments for your environment (here in the NW, I've found no adjustments are necessary to the tollhouse recipe, but Denver required, extra flour and an extra egg for the same chewy texture as no adjustments here) if necessary, and make sure you're baking in a preheated oven that is the right temperature. You'll get it all worked out after a batch or two, and then make notes and just stick with the plan and you'll be very happy with the results.
