Dice up the potatoes into 1' cubes. Bring a large pot of water to a boil, salt the water generously.
Boil the potatoes for 6-8 minutes or until fork tender, then drain and scatter them on a parchment lined baking sheet.
Preheat an oven to 425F. Toss the potatoes in avocado oil, salt and pepper. Roast for 20 minutes or until golden brown, tossing halfway through. Remove them from the oven but leave the oven on.
Let the potatoes cool slightly, before adding them to a bowl with the egg and the vinegar. Generously add in a few twists of pepper and half mash/half mix the mixture together, until it is chunky.
Pour this mixture onto another parchment lined baking sheet and form into a connected sheet of potato. It should be about 1cm high. Season with salt and put back in the oven.
Roast this potato mixture for another 20-25 minutes or until golden on top.
Slice into triangles and serve!