In general, Irish sugar has a very coarse crystal. Irish sugar used to be made from sugar beets, not cane, but there is no appreciable taste difference. Our caster sugar has a finer crystal; the name comes from the fact that this finer sugar could go into a “caster,” or sugar shaker. Caster sugar is the closest to American style sugar, but any white sugar is interchangeable, unless you’re using it as a decoration to top baked goods. In that case, you’d need a large-crystal decorating sugar to sprinkle on top of buns or cakes to get similar results to Irish sugar. The Irish don’t use much brown sugar. Golden demerara sugar is a cane sugar, unrefined so it retains the natural brown color of the dark cane syrup. It’s unlike American light and dark brown sugar, which get their color from molasses added back to white sugar. Turbinado sugar is nearly the same, but you can substitute light brown for demerara.