You will need some puff pastry for this one.Fry some sliced onions and garlic in butter. Add a spoonful of flour and stir in. Add any uncooked leftover vegetables you have (if your veg are already cooked add at the same time as the cooked meat). Put into a pie dish, add some gravy or stock. Top with puff pastry, put some slits in and brush with milk. Bake in oven at 200C for 10 mins then at 180C for 25 mins until pastry is golden brown and filling is done.