Grate the potatoes using a grater and place them in a bowl of water.
After 30 minutes, remove them from the water and dry them off. This is easiest done by placing them in a sieve and shaking off the water.
Dry them with a tea towel and season with salt and pepper.
Place the potatoes in ring molds on a pan and ensure they are at least 4-5 cm high.
Pour the fat into the pan and fry them at high heat for 10 minutes, then reduce to low heat.
Make sure to pour some of the fat on top of your rösti periodically, and 10 minutes before they are done, you can remove the ring mold and flip them. If you do this too early, they will fall apart.
Place them in a tea towel/paper towel to remove some of the fat.
Season again with salt and pepper and serve.