Step 1: Prepare Potatoes and Onion

Peel the potatoes and the onion. Cut the onion in half and peel it.

Step 2: Grate Vegetables

Place a tea towel or dishcloth on a waterproof cutting board. Using a box grater, grate all the potatoes and onion through the coarse grating side onto the cloth. This process should take about 4 minutes.

Step 3: Remove Excess Water

Gather up the tea towel with the grated vegetables and twist and squeeze out as much water as possible into a large bowl. Continue twisting and squeezing until every last drop of water is removed.

Step 4: Prepare Egg and Season

Transfer the now dry grated vegetables into a clean bowl and loosen them. Crack one medium egg into a separate container and whisk it until loose and runny. Add about 1/4 teaspoon of salt and plenty of ground white pepper to the grated vegetables and mix well. Finally, pour the beaten egg over the mixture and mix thoroughly until evenly combined.

Step 5: Heat Pan and Add Fats

Place a 12-inch cast iron frying pan on the stove and heat it until hot. Add 2 tablespoons (30g) of cooking oil and half of the 30g (1oz) butter to the hot pan. Allow the butter to melt and foam.

Step 6: Form and Fry Hash Browns (First Side)

Divide the hash brown mixture into four equal portions. Grab one portion and form it into a round patty. Carefully place it into the hot oil and butter in the pan. If any bits break off, gently push them back into place. Repeat for the remaining three portions. Gently press down each hash brown with a fish slice or flipper. Fry for 6-7 minutes on this side until golden brown and crispy.

Step 7: Flip and Fry (Second Side)

Once the first side is golden brown, flip each hash brown over. Add the remaining half of the cooking oil and butter to the pan. Fry for another 6 minutes on the second side until golden brown and crispy.

Step 8: Drain and Serve

Once both sides are golden brown and crispy, remove the hash browns from the pan and place them on a plate lined with kitchen paper to drain any excess oil. Transfer them to a serving plate and garnish with a little chopped rosemary, if desired. Serve immediately.

• Use a high-starch potato variety like Maris Piper (UK) or Russet Burbank (USA) for best results.

• Squeeze out as much water as possible from the grated potatoes and onions to ensure crispiness.

• Do not add more than 1/4 teaspoon of salt initially, as too much salt will draw out more moisture from the vegetables.