Bannocks are flat cakes of barley or oatmeal dough formed into a round or oval shape, then cooked on a griddle (Scots: "girdle"). The most authentic versions are unleavened, but from the early 19th century bannocks have been made using baking powder, or a combination of baking soda and buttermilk or clabbered milk. Before the 19th century, bannocks were cooked on a bannock stone (Scots: stane), a large, flat, rounded piece of sandstone, placed directly onto a fire, then used as a cooking surface. Several varieties of bannock include Selkirk bannocks, beremeal bannocks, Michaelmas bannock, Yetholm bannock, and Yule bannock.