If you want to cut potatoes in advance, next time cover them with cold water and sprinkle a little salt into the water. Stir the potatoes to make sure that they are completely covered by the cold salt water. Rinse the water off completely, rinse under cold water a few times, drain all the water off them, and store in a covered container in the refrigerator. When you are cooking your meal, leave the potatoes in the refigerator until you are ready to add them to whatever it is you are making. If you take them out of the refrigerator and leave them on the counter while you are preparing, you will get some black spots. If you have everything ready, and just dump them into the pot, you shouldn't have any of those dreadful black spots. A restaurant owner I know taught me this little trick. It works for sweet potatoes and apples too. You won't get the browning. It doesn't alter the taste at all. Happy cooking!