I can only think of two offhand:

The biscuits in Blind Boy Fuller's "Your Biscuits Are Plenty Big Enough for Me" are strictly metaphorical.

"How Many Biscuits Can You Eat" was a hit for Stringbean and others ...

There's a floating verse in Appalachian folksong, too:

Bake them biscuits good and brown,
Lay them sweet potaters round and round.

None of these, however, seems quite what you're looking for. I suggest you look in early country music (roughly 1920s-1950s), if you allow that within your definition of folk songs.

Bob