Ingredients

Steps

• Fry sliced onions in olive oil over low heat for 30 minutes until soft and colored.
• Season onions with salt and pepper and transfer them to a bowl.
• Heat butter in a frying pan until it begins to foam.
• Season liver with salt and pepper and cook in butter for 20 seconds.
• Drain the liver using a colander.
• Return onions to the pan and toss until golden brown and slightly scorched.
• Add the liver and parsley back to the pan and stir in the vinegar before serving.