It's best to leave any preconceptions at the door when it comes to soda bread, because they're probably wrong. This is especially true when it comes to ingredients. Colman Andrews, editorial director at The Daily Meal and author of The Country Cooking of Ireland, writes, "True soda bread is the simplest of things: bread made with nothing more than flour, salt, sour milk or buttermilk, and — in place of yeast — baking soda, which reacts with the milk to have a leavening effect."
What many Americans have experienced, though, is basically cake. It's got raisins or currants and it's softened up with eggs. This is fine, but should really be called spotted dog or railway cake, says Andrews, not soda bread, or traditional Irish soda bread.