Those clever Irish folks are having a bit o' fun at your expense. Bread soda is bicarbonate of soda or baking soda, which you can find in every supermarket. Baking powder, at one-quarter the strength of baking soda, will not do the job.

Tim Allen, author of The Ballymaloe Bread Book, says soda bread became popular in Ireland in the early 1800s when baking soda became widely available. It is also called soda cake, and is still very popular, although it is made with buttermilk these days instead of sour milk.

White soda bread is made with plain flour, while brown is generally made with equal parts of plain flour and whole-wheat flour.