Peel and chop up the potatoes into large chunks and put on too boil in a pot. This will take about 20 minutes. While the potatoes are cooking, you can start cooking the meat.
Chop up the onion and fry in a pan until almost golden brown. Add the ground beef and break it all up and cook until no longer red in colour.
Turn on the oven and preheat a deep baking dish in there.
Add the vegetable cube and make sure it is broken up and mixed inches
Throw in the peas and mix them into the meat and continue to simmer. At this point, you can add a teaspoon or two of browning or seasoning sauce to the meat, and tip in some of the water from the potatoes. Keep simmering the meat in the pan.
The potatoes should be almost cooked - you can test them by sticking a knife into them. If the knife sinks in easily, they're done. Pour off the water and save some of it in case you need more for the meat / sauce.
Mix up two tablespoons of corn-starch with two tablespoons of cold water in a saucer. When it's all mixed into a white liquid, pour this into the meat and stir in quickly. The water in the dish will thicken, continue to simmer and stir occasionally to make sure the corn-starch is cooked through.
Mash the potatoes with a little milk and butter. Take the baking dish out of the oven, and pour in the meat. It will make a satisfying sizzle. Spoon the mashed potatoes on top of the meat until they fill the baking dish to the top. Use a folk to make ridges all along the top of the potatoes.
Put the dish back under the grill and brown the top of the potatoes.