Steps

Shred the potatoes on the large holes of a box grater

Rinse shredded potatoes to remove excess starch until water is clear. Squeeze the potatoes very dry with a towel so the potato can crisp up well. Excess water delays browning and keeps the surface cooler longer, so the potatoes absorb oil and end up greasier. Add salt and mix in

To get the potatoes even drier, let the salted potato sit for 5 minutes to draw out more water, then squeeze again in a towel. You can also spread the potatoes in a thin layer and either let them sit 5 minutes or microwave for about 30 seconds so they start steaming and water escapes

Heat a skillet over medium-high with add oil and butter until shimmering. Add potatoes in an even layer ~1cm thick and press gently. Cook on both sides without moving until deeply golden brown ~5 minutes/side

Remove from pan and season with salt and pepper