The secret to perfect hash browns is to use cold baked potatoes.
3 tablespoons butter
1 cold baked potato, finely grated
salt and pepper to taste
Melt 1 tablespoon butter in cast-iron or other skillet. Evenly distribute potatoes in pan. Fry potatoes slowly and dot with rest of butter as they cook. Cook on only one side. Remove from pan when potatoes are cooked through and bottoms are browned.