In a bowl, mash the potatoes with the butter and salt.
In a large pan, heat up the oil, add the onion, beef and pepper. Sauté for 5 minutes.
Grease a baking form (we used individual baking dishes). Put half the potatoes in the bottom of the dish.
Add the meat and cover with the rest of the potatoes. Smooth the surface. Cover with beaten egg and sprinkle with the cheese.
Bake on a previously pre-heated oven at 180°C for around 30 minutes or until the surface is golden brown.