Place the potatoes in a pan of water. Bring to the boil and cook until tender.
Meanwhile, add the carrots to a small saucepan. Add water to just cover the carrots. Bring to the boil and cook until tender. Do not drain the water.
Add the onion with a little oil to a large deep saucepan over medium high heat. Once soft add the mince and fry until browned. Remove from heat and crumble in the stock cubes; stir well. Sprinkle over the flour and stir well until there are no lumps of flour.
Add peas and the carrots along with the water they were cooked in to the beef mixture. Stir well, season with black pepper and return to the heat on a gentle simmer for 5 to 10 minutes.
Drain the potatoes and mash with milk and butter.
In a deep baking dish place the meat mixture and smooth out. Top with the mashed potato and level out with a fork. Sprinkle over the grated cheese.
Bake in a preheated 200 degrees C oven for 15 to 20 minutes, or until the cheese is golden brown.