Wash, peel, and boil the potatoes, then mash them.
Finely chop the onion and beef, season with salt and pepper.
Heat oil in a pan and sauté the onion and beef.
Mix the mashed potatoes with the sautéed meat.
Place the mixture in an oven-safe dish and smooth the top.
Bake in a 200°C oven for 20 minutes to finish.