Wash, peel and grate the potatoes. Squeeze out as much liquid as possible from the grated potatoes then discard the liquid.
Put the potatoes into a large mixing bowl and season with salt and pepper to taste and stir until well combined.
Heat one-third of the butter with 1 tablespoon olive oil in a nonstick frying saucepan over medium heat until it starts to foam. Take 1/3 cupful of the grated potatoes and put into the frying pan. Flatten out with a wooden spoon.
Cook for 5 minutes on each side or until it turns golden. Transfer mixture to a baking tray and keep warm in a preheated oven at 120°C.
Repeat the process with the remaining mixture, adding butter and oil as required.