Peel the potatoes and grate them using a box grater or food processor. Place the grated potatoes in a clean kitchen towel and squeeze out as much moisture as possible.

Transfer the grated potatoes to a large bowl. Add the chopped onion, flour, salt, and black pepper. Mix well until all ingredients are evenly combined.

Heat a large skillet over medium-high heat. Add the vegetable oil and butter, allowing the butter to melt and mix with the oil.

Divide the potato mixture into 4 equal portions. Shape each portion into a flat patty, about 1/2 inch thick.

Carefully place the patties into the hot skillet. Cook for about 4-5 minutes on each side, or until golden brown and crispy.

Once cooked, transfer the hash browns to a paper towel-lined plate to drain any excess oil. Serve hot.