Preheat the oven to 180°C.
In a large skillet, heat oil over medium heat and sauté onions until golden brown.
Add minced beef and cook until browned and cooked through.
Stir in flour and cook for an additional 2 minutes.
Add beef broth, Worcestershire sauce, and peas. Simmer for 10 minutes until thickened.
In a separate pot, prepare mashed potatoes according to package instructions.
Transfer the meat mixture to a baking dish and spread the mashed potatoes evenly on top.
Bake in the preheated oven for 25-30 minutes, until the potatoes are golden and crispy.
Serve hot and enjoy this comforting British dish.