Preheat oven to 180C/160C fan forced.
Heat the oil in a frying pan over medium heat. Add the onion, carrot and celery. Cook, stirring, for 5 minutes or until softened.
Add the mince and cook, using a wooden spoon to break up any lumps, for 5 minutes or until browned.
Add the flour and cook, stirring, until well combined.
Add the stock, wine, Worcestershire sauce, tomato paste and bay leaves. Stir to combine. Cook, stirring occasionally, for 15 minutes or until the sauce thickens.
Stir in the peas. Season. Transfer to a 3L (12 cup) ovenproof dish.
Meanwhile, cook the carrots and sweet potato in a large saucepan of boiling water for 15 minutes or until tender. Drain. Return to the pan. Mash until smooth. Season.
Spoon the mash over the mince mixture. Brush with melted butter. Bake for 25-30 minutes or until golden.
Sprinkle with parsley to serve.
