what is barm
barm - a commercial leavening agent containing yeast cells; used to raise the dough in making bread and for fermenting beer or whiskey. yeast. yeast cake - small cake of compressed moist yeast. brewer's yeast - yeast used in fermenting beer. leaven, leavening - a substance used to produce fermentation in dough or a liquid. mother - a stringy slimy substance consisting of yeast cells and bacteria; forms during fermentation and is added to cider or wine to produce vinegar.
Barm cake. A barm cake is a soft, round, flattish bread roll from northern England, traditionally leavened with barm. Chips are a popular filling, sold in most fish and chip shops in the North West of England often called a chip barm. Another popular filling in the Northwest, particularly Bolton, is the pasty barm.