I always use half butter and half shortening in my cookie recipes that call for all butter or butter-flavored shortening. I have never had a bad batch. Every time I use all butter, the cookies spread too much and they cook too fast and become too crispy (I like my cookies soft and chewy). I bought some Crisco butter-flavored shortening a while back and was grossed out by it. The fake color and the smell was too much for me to stomach. Somehow, the traditional vegetable shortening doesn't bother me. Anyway, go for the butter/shortening combination. I hope your cookies turn out as good as mine always have.
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