Let me start out by saying that I am a very experienced cook & baker, I know better to make these kinds of mistakes. I was baking cookies with my daughters last night. Let's just say they didn't turn out as planned. The cookies ended up being very flat & crispy compared to the nice thick chewy ones we love. They actually tasted alright, a little greasy but edible. I made the number one mistake anyone could make when baking, I didn't read the recipe or ingredients correctly.
I didn't have any shortening so I substituted lard. That in itself wasn't the problem. I was distracted and had a migraine so after double checking that I could substitute the lard equally for shortening, I used 1 cup lard in place of shortening. Theoretically that was ok too. The problem was that the recipe only called for 1/4 cup shortening. I was looking at the wrong line on the recipe. Crap!
Tell me what kind of rookie mistakes have you made in the kitchen when you totally know better?