Parboiling potatoes simply means boiling them until they are partially cooked. Given that nobody wants to eat partially cooked potatoes, the technique is always a precursor to a secondary cooking method, usually a high-heat method such as roasting, deep-frying, pan-frying or grilling.
Parboiling is a similar technique to blanching. With blanching, you plunge ingredients in boiling water for merely a minute or two to just take away their raw taste. Parboiling usually takes longer, and results in a greater degree of doneness.
Parboiling reduces the total cooking time for many potato preparations. Starting high-heat techniques with partially cooked potatoes makes it easier to achieve crispy edges with fully-cooked, fluffy interiors than if you started with raw potatoes. Parboiling washes away some of the simple sugars present in the potato, resulting in a golden crust rather than a darker brown one.
Parboiling is a simple process, but you do need to pay attention to the potatoes to make sure they don't overcook and become waterlogged. It's your choice whether or not to peel and cut the potatoes.
Transfer the potatoes to a saucepan and cover them with cold water. Add a teaspoon or so of salt.
Put the pan over a high heat on the stove top and wait for the water to come to a boil.
Reduce the heat so that the water is simmering instead of boiling.
Simmer the potatoes for one to 10 minutes, depending on their size. Poke a potato with the point of a sharp knife. The potatoes are done enough if the knife slides into them fairly easily but meets some resistance in the center.
Potatoes or pieces that are approximately the size of a golf ball will need about four minutes of simmering time. Smaller dice or thin French fries may only take a minute.
Turn off the heat, drain the potatoes using a colander and then return them to the dry, warm pan. Allow the potatoes to cool and release their steam for at least a few minutes. Doing so dries the potatoes out, giving them a better chance of becoming crispy when you continue to cook them.
Parboiling is just the first step in many potato preparations. If you are not ready to continue cooking them immediately, store parboiled potatoes in a covered container in the refrigerator for up to two or three days.