The definitive side for Prime steak
Four large or six medium sized potatoes One medium sized onion, finely diced
One pound of unsalted butter
Salt and pepper to taste
Peel and quarter potatoes lengthwise. Boil in salty water until just cooked through. Allow to cool and store in refrigerator over night. Alternatively bake whole, unpeeled potatoes. Score at X on to the top of the potatoes and bake 400°F for two hours, allow to cool. Peel the next day.
The next day dice cooled potatoes.
Clarify butter. Heat butter gently in a saucepan until butter is melted and white foam forms on top (these are the milk solids) spoon this off, what remains should be golden and clear.
Heat a cast iron skillet over medium/high heat. Add clarified butter and once heated sauté the diced onion until translucent and begin to caramelize. Season with salt.
Add diced potatoes, fold into onions, season with salt, press down with spatula to form a cake.
Cook with out moving until you see a deep bronze color (you can peak under the edges).
You have two options here:
Remove from heat, spoon or pour off any extra butter (reserve) Place an inverted plate over pan flip. Pour any reserved butter back into pan. Slide the potatoes back into pan. Cook until browned.
Place pan under broiler. Cook until browned.