Heat the oil in a large saucepan over medium heat. Add half the mince and cook, breaking up the mince with a wooden spoon, for 3-4 minutes or until browned. Transfer to a bowl. Repeat with the remaining mince.
Add celery, carrot and onion to the pan over medium heat. Cook, stirring, for 3-4 minutes or until softened slightly. Add garlic and tomato paste, and cook, stirring, for 1 minute or until aromatic. Return mince to the pan. Add flour and stir until well combined. Add water, stock, Worcestershire sauce and bay leaves, and stir until well combined.
Increase the heat to medium-high and bring to the boil. Add potatoes. Reduce the heat to medium and simmer, stirring occasionally, for 20-25 minutes or until the mixture thickens slightly and the potatoes are tender. Stir in peas and cook for 2 minutes or until heated through.
Sprinkle with parsley and serve with crusty bread, if desired.
