• ¾ cup (or as needed) olive oil
• 4 cups thinly sliced red onion
• ¾ cup partially rendered diced pancetta (see Note)
• ¾ cup (all-purpose) flour
• Salt and freshly ground pepper
• 1½ pounds calves liver, cut into eight ⅓-inch-thick slices
• 1 cup Chicken Stock
• 6 tablespoons hazelnuts, toasted and coarsely chopped

Heat ¼ cup oil in a large sauté pan over medium heat. Add the onions and cook until tender, 7 to 10 minutes; remove from the pan and set aside.

Heat 2 tablespoons oil in the same pan over medium heat. Add the pancetta and cook until lightly browned and almost crunchy, about 5 minutes; remove with a slotted spoon and set aside with the onions.

Season the flour with salt and pepper. Dredge the liver with the seasoned flour and shake off the excess. Heat ¼ cup oil in the same pan over high heat. Add as many slices of liver as will comfortably fit in the pan and sear 2 minutes each side for medium-rare; remove from the pan and keep warm. Repeat with the remaining liver.

Pour off the excess oil, add the stock to the pan and boil, scraping up the browned bits on the bottom, until slightly thickened, about 2 minutes. Return the onions and pancetta to the pan and stir in the toasted hazelnuts. Season to taste with salt and pepper. Arrange 2 slices liver on each plate and spread the onion mixture over top. Serve immediately with roasted potatoes.