Preheat the oven to 425F/220ºC.
Pat the steak cubes dry with a paper towel and season well with salt and pepper.
Add one tablespoon of olive oil and two tablespoons of butter to a skillet and melt over a medium heat.
Add in the cubed sirloin steak and cook until browned on all sides but not fully cooked through
Remove to a plate and set aside.
Add the remaining four tablespoons of butter to the same skillet and allow to melt before adding in the flour and tomato paste. Cook for around one minute then pour in the broth whilst whisking to break up any lumps
Bring to a boil and continue to cook whilst simmering until the liquid has thickened.
Remove from the heat and add in the cubed sirloin steak, frozen vegetables, diced potatoes, thyme and worcestershire sauce. Season with half a teaspoon of salt and a quarter teaspoon of pepper.
Divide the mixture between individual serving dishes and then cut the pastry to fit perfectly in the top.
Brush with the beaten egg and make a few small slits in the top of the pastry to allow any steam to escape.
Bake in the oven for 25 minutes