Parboiling, or partially cooking, potatoes tenderizes them and allows you to roast or pan-fry them more quickly and without overcooking the outsides. If you are boiling whole or large potatoes that have been cut in half, test them after about 7 minutes by inserting a sharp knife in the center. If the knife goes in easily and offers little to no resistance, the potatoes are perfectly parboiled.
You can parboil potatoes with or without the skin. In either case, scrub them well with a vegetable brush and place them in a large pot with enough fresh cold water to cover. Bring the water to a rolling boil on high, then turn the heat down to medium-low and set a timer for around 7 minutes. If you're working with smaller pieces, such as wedges or cubes, start testing the potatoes after about 4 minutes. When done, remove them from the heat, drain them immediately in a large colander and run cold water over them. You can also plunge them into an ice bath, which is called shocking, to stop them from cooking further. Drain again and refrigerate until you are ready to use them, or up to 7 days.