Cooking and baking are so much fun and so educational! I don't know why teachers don't use cooking more in preschool lesson plans. It could be spreading icing on a cookie, making a peanut butter sandwich for lunch, or even making a salad. It adds so much.
In those simple activities what knowledge can they get from that? Well, hand-eye coordination, self help skills, and healthy eating for a start. But if you go a bit deeper, you find they would learn lots of math concepts (measuring, counting, fractions), science (one matter being changed into another by heating or cooling), or pre-literacy(reading a recipe).
So try and work a cooking activity into you lesson plans. It's worth the hassle!