Finely dice the onion and garlic, and add to a frypan with a little oil and lightly brown -- then add the diced beef and cook till browned.
Add onion gravy mix and beef stock mix and combine well.
Add vegetables and cream of mushroom soup and bring to a light boil, stirring constantly -- then add the potato and mix through until gravy is smooth.
Let cook for 20 minutes on low, without a lid. Mixture should be thick and congealed.
Place mixture in a pie dish (you can add a double puff pastry base if you like) and top with a sheet of puff pastry. Cut to size and seal the pie by pinching the pastry down. Brush with egg and cut 4-6 slits in pastry to allow steam to escape.
Place pie on a cookie tray (to catch any drips) and put in a pre-heated oven, 180 degrees C for 30-35 minutes, or until golden brown.