Crisp-bread made from oatmeal, as Havercake or Clapbread
"The riddle-bread, used in Lancashire and Yorkshire, is prepared from oat-meal, leavened by a little sour dough, preserved in the kneading trough from one baking to another. The meal and water are, in this case, mixed thin, and left all night to ferment. Next morning, the dough is poured upon a board, cut by furrows into squares. By a motion similar to riddling corn, the dough is made to expand, hence the name of riddle-bread. Bread thus made is spread upon a cratch, or a frame of wood, crossed with strings. Here the bread becomes very hard, and will keep almost any length of time. Before eating, it is usually toasted by the fire; and, when well buttered, is remarkably pleasant. A gentleman in Lancashire observes, that the proper quantity of butter, is, the same thickness as the bread." - John Briggs, 'Letters from the Lakes', 1825.
The 'Reminiscences of Miss Isabel Dobson (1806-1882)', has "When invited out to 'tea', or an afternoon visit, the fare offered was strong home-brewed beer, with riddle bread well buttered and toasted, broken into it."