Definition of "mushie"

He grabbed a box of mushrooms away from a lady who was crowding past him to look out the window […] and the lady screamed, “Give me back my mushies!”

1980, Stephen King, The Mist

“I'd like sausage, eggs, bacon, toms, mushies, beans – oh, and some fried bread,” said Mike.

2009, Mark Penny, Jonathan Penny, The Golden Pig, page 160