In a nonstick 10-inch saute pan, heat the vegetable oil and butter over medium heat. Press grated potato into pan. Season with salt and pepper. Let cook undisturbed until crisp on bottom, 8 to 10 minutes. Gently flip onto a plate and then slide other side into pan to cook. Salt and pepper second side. Cook another 5 to 10 minutes, until potato cake is cooked through and nicely browned. Cut into wedges, sprinkle with parsley and serve.