Preheat the oven to 200°C. Heat the oil in a pan and fry the onion until soft and golden.
Remove the boerewors from its casing and add the meat to the pan. Cook until browned, breaking it up with a spoon as it cooks.
Stir in the chutney, tomato sauce, and Worcestershire sauce. Season lightly with salt and pepper, then allow the filling to cool slightly.
Roll out the puff pastry and place half into a greased pie dish. Spoon the boerewors filling inside evenly.
Cover with the remaining pastry and seal the edges with a fork. Brush the top with beaten egg and cut a few small slits for steam.
Bake for 30 to 40 minutes until the pastry is crisp and golden brown.