What you need to do first is pre-boil the potatoes. Clean them and slice them if they’re too big in chunks. Not too big, not too small. If they’re too small chances are they’ll mash together and if they’re too big they will be undercooked or raw on the inside. I assume you know your potatoes, so cut them in slices that will not endanger your food in either way.
When you boil them add a bit of oil and salt to the water. Oil will make them absorb anything easier later. While you do that heat up the oven at about 200 – 250 degrees and ready a pan. Next you will need to grease that pan with whatever strikes your fancy. Olive oil is the healthiest thing. Next comes butter, which is my personal favorite. Cut off a chunk and throw it in the pan and spread it around evenly on the bottom of the pan and the sides. For an extra crunchiness, use goose fat. Goose fat is not that health but it will make your potatoes heavenly tasty and crispy.
Let the potatoes boil for about 7-10 minutes. You don’t need to actually boil them through only pre boil them so they’re ready to absorb anything you throw at them. By staying in the oven they’ll cook all the way through, so if you boil them too much at first they’ll just mash. It’s important you put the potatoes in the pan on a single layer, so every one of them is resting on the bottom of the pan, not on top of another potato. Put them in the oven for about 20 minutes. When you take them out you’ll see a crispy crust developing on their upper side. Now comes the best part, the actual tricky part, which is the key element of these potatoes.