My family loves eating Alton Brown’s ‘The Chewy’ chocolate chip cookies. Last Friday, tried making both his puffy and his thin chocolate chip cookie recipes. However, the resulting cookies looked almost exactly the same! When I investigated, it turned out that my baking powder was getting weak (i.e. it foamed gently in hot water, rather than bubbling vigorously), and the puffy cookie used baking powder while the other cookies I’ve been making use baking soda.
I plan to repeat the experiment some other time and post the results then, including pictures and carb counts.
The moral of the story: be careful of the age of your baking powder.