Irish oatmeal, also known as steel-cut oatmeal or pin oatmeal, produces a coarser, nuttier porridge than traditional American rolled oats. This form of oatmeal is produced by hulling the oat and slicing it into multiple pieces rather than flattening it between rollers. Most cooks use Irish oatmeal to make hot breakfast cereals, but you can also use it as a substitute for other kinds of oats. This form of oatmeal can change the texture and cooking time of your baked goods slightly, but it's still an effective addition to many recipes.
Old-Fashioned Rolled Oats
Rolled oats undergo a flattening process during which they are steamed and pressed between two rollers. This makes the oats easier to digest and causes them to cook more quickly. If your recipe calls for this kind of oatmeal, substitute Irish oatmeal cup for cup, but increase the cooking time by 10 to 15 minutes. Check the recipe frequently to keep the food from burning. You can also allow batters and doughs to rest for an hour in order to let the oats absorb more water -- this works better for cookies and other recipes that have a very short cooking time. After resting, bake the recipe according to the directions.
The term "groat" refers to the whole, hulled oat grain. Sometimes used to make very sturdy porridges and baked goods, this kind of oat also works well in soups. You can substitute Irish oatmeal directly for oat groats, but you should expect a slightly different texture. The smaller size of Irish oatmeal causes it to cook more quickly and produce a softer texture overall.
Quick oats are a form of rolled oat that has been treated to make it cook even faster. They have been pressed thinner than old-fashioned rolled oats. Some brands also undergo chopping to speed up the cooking process. It can be difficult to substitute Irish oatmeal for this product without significantly changing the texture of the final recipe. You can pulse Irish oatmeal in a coffee or spice grinder to reduce the size of the particles and bring cooking times closer to that of quick oats.
Also called instant oatmeal, this product is composed of very thin, broken rolled oats. Some brands use steam heat to partially pre-cook the oats, making it possible to produce a breakfast porridge with just hot water. Instant oatmeal products usually contain flavorings and sweetener. When reconstituted, they produce a fine porridge with no identifiable grains. In recipes, instant oatmeal thickens and flavors but adds relatively little texture. To substitute Irish oatmeal for this product, grind the oats to a coarse powder in a food processor or coffee grinder.