Preheat oven to 180°C.
Boil potatoes until soft in salted water.
Drain and mash with milk and margarine until smooth then set aside.
Heat oil in a pot and gently fry the onion until soft.
Add the beef mince and fry until well browned, stirring to break up the mince.
Once the mince is browned stir in the cake flour, KNORR Beef Stock Pot, tomato paste, Worcestershire sauce and Robertsons Mixed Herbs and allow to cook for 2 minutes.
Add the carrots and water and allow to simmer covered for 20 minutes.
Add the frozen peas and allow to simmer for a further 5 minutes.
Spoon the mince into an ovenproof casserole dish, top with mashed potato then sprinkle with grated cheddar cheese.
Bake in a preheated oven for 25-30 minutes until golden brown on top.