Preheat the oven to 220°C.
Heat oil in a pan and brown the beef, followed by the kidneys.
Add diced onions to the pan and cook for 4 minutes.
Return the beef to the pan and coat everything with flour.
Stir in 850ml of beef stock and bring the mixture to a boil.
Simmer uncovered for 90 minutes, adding more stock if the liquid evaporates.
Season with salt, pepper, and Worcestershire sauce, then let the mixture cool.
Transfer the meat into a pie dish.
Roll the pastry to 5mm thickness, making it 5cm wider than the dish.
Cover the dish with pastry and crimp the edges to seal.
Brush with beaten egg and bake for 40 minutes until golden.
Serve with mashed potatoes and steamed vegetables.