It seems like that would be important.
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I don't know what oil Big Mama used. I wanted to get the answer from the recipe author. It could be any oil but I think the type of oil would be important for the recipe. Many old timers used Crisco.
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That does seem like an important question. Authors don't always see the Hotline questions. You can send her an email message by clicking on her name and then on the email icon. Let us know what she says.