2 pounds russet potatoes, peeled and sliced into 1/4" rounds
3 tablespoons butter
3 tablespoons olive oil
2 small yellow or sweet onions, thinly sliced
1/4 cup parsley, chopped
Kosher salt and pepper, to taste
Add sliced potatoes to a pot of water and cover with cold water. Bring to a boil, reduce heat and let simmer for 4 minutes. Drain well.
Heat 1 tablespoon butter and 1 tablespoon oil in a large nonstick skillet until shimmering. Add 1/2 potatoes and 1/2 of the onions. Let cook until potatoes are starting to crisp and the onions are golden, about 15 minutes. Add the rest of the butter, oil, potatoes, and onions and continue to cook, mixing until all onions are softened and browned, about 15 minutes.
Remove from heat and garnish with parsley. Season with salt and pepper and serve.